There is a small town in Poland called Miejsce Odrzanskie, where no boys were born for approximately 15 years. Throughout that time, 12 girls were born in that village with 343 inhabitants. The story quickly traveled around the world, and a large number of theories and debates developed around it. Modern genetics is a rapidly advancing science with new findings emerging constantly. However, humanity still knows very little about the factors that may influence a child’s sex. Therefore, it may be critical to utilize every opportunity in order to broaden the knowledge regarding such an unstudied field. Even though a significant number of studies were conducted, results are frequently inconsistent and contradict each other. Nonetheless, there are several limitations, which may considerably decrease the scientific value of the above-mentioned phenomenon.
Potential Value of the Phenomenon
On the one hand, even though the case dragged a significant amount of attention worldwide and became a highly debatable topic, its scientific value may be questionable. The main limitation of any studies related to Miejsce Odrzanskie is a relatively small population. Studies that rely on small samples may provide inconsistent results and have no statistical value. There were only 12 consecutive female births in the town. Even though it may seem to be a significant number with a low probability for such a small village, it does not appear as impossible in terms of the global population. The chance that all children in a randomly selected sample of 12 newborns would have the same sex is 1 in 4096. It is a relatively low probability on the scale of a small village, yet it is big enough to occur frequently. The number of children born every day may differ considerably from one source to another. Nevertheless, in most cases, these numbers are close to 300,000, which means that 12 consecutive births of same-sex children occur approximately 73 times every day. It may not be rational to call an event that occurs with such a significant rate a statistical abnormality.
On the other hand, as already mentioned, it may be vital to use every opportunity to provide further research on the topic. Therefore, the phenomenon may contain sufficient scientific value to be studied. It may be beneficial to investigate different specific factors, including local ecology, unique traditions or daily routine activities, and maternal nutrition. The interrelation between such factors and the child’s sex is frequently investigated, yet collected data is inconsistent and hence, unreliable. However, it may also be necessary to understand the limitations of such a study and consider the possibility of a coincidence. It may be essential not only to study the phenomenon but also to continue using other opportunities in order to increase knowledge.
Hypotheses
The first hypothesis that may shed light on the possible origin of the phenomenon is a statistical error or a coincidence. As already mentioned, the probability of such a phenomenon is relatively high. Moreover, it may be linked with other factors such as the migration of people from the town. There is a chance that people who moved away recently have boy children, yet they are not reflected in the statistical data. The probability of such statistical errors may also serve as an explanation of the phenomenon.
Another hypothesis that may explain the nature of the phenomenon is closely linked with the above-mentioned factors that may influence the child’s sex. For instance, evolutionary theories imply that the amount of accessible food and other elements of the external environment may impact the birthrates of males and females. In most cases, such evolutionary features become rudimentary and may correlate with emerging tendencies. For example, extreme modern diets may be perceived by the organism as an indicator of insufficient food availability resulting in a shift of sex ratio. Even though a recent study has shown that the interrelation between material nutrition and sex ratio is insufficient, there may be other factors that influence the sex of a future child (Kermani & Nematy, 2017). Furthermore, it was identified that malnutrition might have a noticeable impact on the sex ratio (Kermani & Nematy, 2017). Therefore, it may be possible that a certain factor or a combination of factors triggers a rudimentary feature that developed in the process of evolution. It may also explain the complexity of studying the phenomenon as such evolutionary features are frequently hard to determine and research.
Conclusion
The phenomenon should be investigated through the prism of population genetics as it focuses on various phenomena, including adaptation, speciation, and population structure. The case phenomenon correlates with the field of population structure. Moreover, according to one of my hypotheses, it may represent adaptation mechanisms. Studying such cases may contribute not only to a more comprehensive understanding of factors that may influence a child’s sex but also provide an opportunity to develop new findings related to the evolutionary nature of reproductive mechanisms. Hence, even though the above-mentioned phenomenon may represent a statistical coincidence, it may be essential not to miss a research opportunity if it offers one.
Genetic diversity refers to genetic variations within a population or species of a given organism and it has been shown to offer the amphibians protection against environmental adversaries. Research has shown that the wood frogs (Rana sylvatica) that have a lower genetic diversity are more susceptible to the negative effects of ultraviolet- B radiation than those having a higher genetic diversity. In the experiment done, frogs eggs and larvae were exposed to three different conditions that included; unfiltered sunlight, sunlight filtered through a UV-B blocking filter (Mylar), and through a UV-B transmittin known as acetate. The findings showed a negative relationship between genetic diversity and egg mortality, larval mortality, and defog filter city rates. It showed that the UV-B radiation causes an increase in egg and larval mortality rates and it also increased the number of deformities in amphibians.
Amphibians have been shown to be declining in numbers across the globe and the reason for this could be as a result of loss of genetic diversity among these amphibians. The reasons for this loss is as a result of habitat fragmentation because many of the amphibians are highly philopatric, have short natal distances due to their small sizes, experience low dispersal across habitats because they require moist habitats, and, lastly, the amphibian populations undergo fluctuations from year to year which gradually leads to loss of genetic diversity.
The amphibians are getting exposed to increased amounts of radiation (280-320 nm wavelength) that are reaching the earth’s surface due to the depletion of the ozone layer. The global increase in UV-B radiation has made researchers hypothesize it as the reason behind the global decline in the population of amphibians. Some research done in trying to explain the reason behind the declining numbers of amphibians has shown a level of synergism between the UV-B and diseases, low PH, and harmful chemicals. This study though is trying to show the synergism between the UV-B and low genetic diversity as possible proof of the hypothesis that the UV-B could be the possible cause of declining amphibian populations.
The hypothesis for this research was that the genetically diversified amphibians exhibit a higher resistance to the UV-B than the less genetically diversified ones. The hypothesis was tested on the wood frogs (Rana sylvatica). Wood frogs were collected from twelve amphibian populations; their genetic diversity was then analyzed after which they were subjected to three different UV-B treatments discussed above. The eggs were collected from the woodlots that interspersed the row crop agricultural fields. The distance between one population of wood frog population to the next was measured as 441m between two woodlots. The genetic structure of the wood frog population was then analyzed using Randomly Amplified DNA markers (RAPD).
Genetical diversity estimates for 12 populations of wood frogs were obtained in 12 separate island woodlots. The eggs were collected from the ponds and about thirty of them per pond, a maximum of 25 egg masses from each pond were sampled. The eggs from each egg mass were then placed in a separate plastic container with pond water and then transported to the laboratory where they were grown under controlled laboratory conditions. Three eggs from each egg mass were maintained in order to counteract possible problems that could occur during DNA extraction. The eggs were then subjected to Mylar, acetate and direct sunlight treatments. The UV-B measurements of the experimental room was about 25-285µ W/cm2 and the Mylar filters blocked 90% of the UV-B while the acetate filters blocked about 36% of the UV-B.
Most mortality occurred at the larval stage and 186 tadpoles were deformed, 4 of them showed signs of edema, 181 had axial malformations and 1 had both axial malformation and edema. Exclusion of the sun treatment resulted in lowered mean larval mortality and deformity rates and a slightly increased egg mortality rates.
The data indicates that a synergistic interaction between the UV-B and the genetical diversity amphibians can influence amphibians’ fitness. The findings of the research were that UV-B has a significant effect on the survival of wood frogs; under the UV-B transmitting filter (acetate), the mean larval mortality rate was 8 times higher and mean deformity rates was about 10 times higher than under the UV-B blocking Mylar. The study also showed that the egg mortality was not really affected by UV-B treatment. The study also provides evidence to support the hypothesis that genetic diversity alone affects egg mortality, larval mortality and deformity rates in wood frogs.
From this study, one can confidently conclude that the interaction between the UV-B and the genetical diversity has a significant influence on the survival of the wood frogs. The UV-B radiation affects the larval mortality rates and increases the deformity rates but does not affect egg mortality in any significant way.
Using current research literature on behavioral issues and novel treatments for Down syndrome, this paper explores and discusses behavioral inflexibility, restrictive and repetitive behaviors, and Down syndrome’s neurogenetic nature. Behavioral flexibility or the ability to provide adaptive responses to spatially or temporally unstable and variable environmental conditions can be crucial to social success but is lacking in the discussed condition. Restrictive and repetitive behaviors or RRBs are a class of behavior-related issues manifested in Down syndrome and autism spectrum disorders. Possible genetic treatments, such as chromosome silencing techniques, could prevent these symptoms’ development but might be ethically imperfect by slightly increasing the risks of miscarriage and infection. Aside from treatment, the findings from Harrop et al. (2021) and Riggan et al. (2020) could improve counseling psychologists’ recognition of challenges affecting Down syndrome patients’ families.
Introduction
Down syndrome has pervasive influences on child development, behaviors, and a degree of independence. Extensive research has been conducted to develop and propose effective treatments for the condition. As a neurogenetic disorder causing intellectual disability, Down syndrome involves behavioral inflexibility and restrictive/repetitive behaviors, and the possibility of mitigating these and other symptoms through prenatal chromosome silencing techniques provides a promising yet ethically controversial avenue of research.
Down Syndrome and Its Behavioral Impacts
Insufficient Behavioral and Cognitive Flexibility
In Down syndrome, behavioral inflexibility is closely intertwined with cognitive inflexibility, or the cognitive system’s reduced ability to adapt to new events. This includes difficulty switching between tasks and maintaining several concepts simultaneously (Harrop et al., 2021). In trisomy 21 patients, both cognitive and behavioral flexibility is reduced, resulting in deficient adaptability. Regarding the cognitive component, deficits in executive functioning in pediatric patients with this diagnosis are well-established (Harrop et al., 2021). Harrop et al. (2021) effectively demonstrate high behavioral inflexibility scores in children with trisomy 21. It is, however, pointed out that their behaviors are still more flexible than those of their peers having fragile X syndrome and autistic spectrum disorder simultaneously.
Interestingly, as a feature of Down syndrome patients, behavioral inflexibility might not be exclusively negative for mental well-being. While also present in typically developing individuals, it could serve some protective purposes in both neurotypical children and their peers with Down syndrome. Specifically, inflexible behaviors in Down syndrome and typical development can instrumentalize predictability as an anxiety coping mechanism (Harrop et al., 2021). This, however, does not deny the issue’s detrimental impacts on socialization and communication.
Restrictive and Repetitive Behaviors (RRBs): Manifestations and Influences
RRBs can permeate multiple areas of activity and everyday tasks, resulting in repetitive purposeless movements, echolalia or meaningless repetition of phrases heard from other people, rituals, the unwillingness to alter any routines, and similar issues. In children with Down syndrome, lower-order behaviors, such as primary motor stereotypies, are more widespread compared to higher-order ones, such as a preference for rituals and the presence of circumscribed interests (Harrop et al., 2021). Notably, individuals with other neurodevelopmental conditions aside from trisomy 21 or typically developing children can also exhibit RRBs (Harrop et al., 2021). Due to this, establishing the underlying causes of RRBs in Down syndrome could be challenging.
RRBs’ influences on the developing individual’s social and academic life are enormous. The early manifestations of RRBs, in the form of behaviors of the higher- and lower-order classes, are predictive of maladaptive and problematic behaviors later in life (Harrop et al., 2021). In Down syndrome patients, the signs of insufficient adaptation can be vastly diverse, including externalizing and internalizing symptoms, aggression, oppositional behaviors, inattention, and so on.
Even in school-aged children with high-functioning trisomy 21, as their parents report, such problematic behaviors create substantial barriers to social integration, learning, and interpersonal communication (Riggan et al., 2020). Regarding learning, in their study that compares inflexibility scores for trisomy 21 and fragile X syndrome children, Harrop et al. (2021) demonstrate that redirection can be the most challenging in the first group. Although studied in the context of parent-child interaction, this fact could have implications for academic progress, including difficulties in activities requiring multitasking.
Down Syndrome as a Neurogenetic Disorder and Possible Implications for Therapy
Chromosomal Silencing: Benefits and Ethical Challenges
Down syndrome’s nature involves some opportunities for prenatal genetic interventions that could reduce behavioral and other symptoms’ manifestations. Being among the most common neurogenetic disorders, Down syndrome affects 1 in more than 800 children and is caused by one extra copy of human chromosome 21 (Riggan et al., 2020). Trisomy silencing and its effectiveness have become prominent avenues of research relatively recently.
In a range of preliminary studies published between 2012 and 2015, it has been shown that prenatal interventions involving silencing the extra chromosome or gene targeting could alter gene expression to promote more typical cognitive and socio-emotional development (Riggan et al., 2020). Therefore, in-utero chromosomal silencing could potentially erase behavioral and cognitive differences between typically developing children and those with Down syndrome.
Despite not being actually used in Down syndrome treatment, prenatal genetic interventions introduce various ethical concerns. Firstly, although expected to promote better adaptability, prenatal genetic therapy could have poorly explored long-term effects, thus creating a sense of uncertainty and moral suffering for parents (Riggan et al., 2020). Secondly, in-utero treatment might slightly increase the risks of miscarriage and maternal and fetal infections, making many parents reject this hypothetical scenario (Riggan et al., 2020).
Finally, in spite of these risks, genetic therapies do not guarantee sensible results in developmental symptom prevention. Considering Down syndrome’s severe differences from life-threatening and terminal illnesses affecting children, the risks above might be considered elevated, so future research should focus on hypothesizing such interventions’ developmental side effects and clarifying risk-benefit ratios.
Counseling for Down Syndrome and Special Needs Patients
Regarding practical implications, the information above and knowledge of developmental disorders will support me in counseling Down syndrome and special needs patients in my future career as a psychology major. To start with, an understanding of Down syndrome’s effects on behavioral flexibility and adaptability will promote the recognition of functional and psychological deterioration in special needs populations, resulting in timely referrals to other services. At the same time, these findings strengthen the knowledge of behavioral inflexibility as a concern requiring accommodations and strategies to create less unpredictable environments for special needs children. This will enhance therapeutic communication at the family level by improving the recognition of such families’ struggles.
Conclusion
In summary, Down syndrome’s behavioral symptoms are not conducive to successful learning and communication, thus causing the need for new treatments, including prenatal chromosomal silencing. This intervention type is, however, fraught with diverse ethical concerns, ranging from miscarriage risks to limited effectiveness. By explaining psychological challenges associated with the diagnosis, these findings are of practical value to counseling psychologists providing services to special needs populations.
References
Harrop, C., Dallman, A. R., Lecavalier, L., Bodfish, J. W., & Boyd, B. A. (2021). Behavioral inflexibility across two neurogenetic conditions: Down syndrome and fragile X syndrome. American Journal on Intellectual and Developmental Disabilities, 126(5), 409-420. Web.
Riggan, K. A., Nyquist, C., Michie, M., & Allyse, M. A. (2020). Evaluating the risks and benefits of genetic and pharmacologic interventions for Down syndrome: Views of parents. American Journal on Intellectual and Developmental Disabilities, 125(1), 1-13. Web.
Medical and genetic consultation means an examination by a geneticist and a specialized medical institution. Consultation with a geneticist necessarily begins with clarifying the diagnosis of the proband. In genetic counseling, technical methods are used: clinical and genealogical, cytogenetic, biochemical, and molecular-genetic. If necessary, doctors of other specialties are involved in the examination of the patient. Various methods of available clinical and laboratory research are often used: hormonal, radiological, immunological, etc. A genetic specialist needs to know the correct algorithm of actions in genetic counseling to avoid possible adverse reactions. The procedure of genetic counseling plays a significant role in family planning and the prevention of possible genetic diseases in children.
Genetic counseling originated in the United States about fifty years ago and has acquired many new features over the past thirty years. According to Abacan (2019), “genetic counseling is the process of helping people understand and adapt to the medical, psychological and familial implications of genetic contributions to disease” (para 1). The main tasks of medical and genetic counseling are to establish an accurate diagnosis of hereditary pathology and prenatal diagnosis of congenital and hereditary diseases by various methods (Abacan et al., 2019).
In 2018, genetic counseling became a healthcare profession and was represented in many medical specialties, such as obstetrics, pediatrics, oncology, cardiology, and neurology (Owens et al., 2019). The development of this science is significant for the prevention of various genetic diseases.
The purpose of this paper is to consider the case of a patient who may need genetic counseling. This paper describes the reason for genetic counseling, which is based on familiarization with the patient’s medical history. There is also a discussion of the patient’s probable reaction and methods of avoiding an adverse reaction. In addition, there is a proposal regarding health issues, prevention, screening, diagnosis, and prognosis. The procedures and effectiveness of the treatment provided to the patient are discussed. This paper uses other studies and related literature to reveal this topic better.
Reason for the Genetic Counseling
Mrs. Falls is a 41-year-old woman from Virginia, USA, who presented with a Family Health History assessment (FHH) that showed that she has a high probability of having a child with Edwards syndrome. Mrs. Falls stated that there were no genetic diseases in her family. Her father died of heart failure, and her mother died of severe and neglected pneumonia. However, her cousin’s brother was born with Edwards syndrome, which caused the patient concern. Mrs. Falls had such bad habits as smoking and drinking alcohol, and she also suffered a sexual infection with damage to the reproductive organs. Mrs. Falls decided to check her suspicions for possible illnesses, and her fears were confirmed with the help of the Surgeon General’s Family History Tool.
Genetic counseling has many reasons, such as preventing a specific health condition, planning a pregnancy, or a life partner. Edwards syndrome is a severe congenital disease caused by chromosomal abnormalities. Unfortunately, this disease cannot be cured, but only its consequences can be alleviated (Hoon et al., 2018). Mrs. Falls was concerned about possible illnesses caused by a previous sexual infection and a similar case in her family.
Now she has confirmed this at a consultation, and she will be asked to share the results with her doctor during the next visit. It is necessary to provide complete information about the family’s medical history. It will help the doctor understand what screening tests the patient needs and when they should be performed (Ginsburg et al., 2019). This test can help Mrs. Falls’ doctor provide her with the utmost care and treatment. The doctor can recommend actions to reduce the likelihood of Edwards syndrome in the patient’s children with the necessary information.
Possible Reactions the Patient May Have/How to Avoid Negative Reactions
Often, people who turn to a genetic consultant experience a high level of anxiety, which should not be forgotten. Such pressure can be challenging to overcome, so it can significantly affect the patient’s emotional state. A genetic consultant should help the patient cope with strong feelings that can cause the results of a genetic examination. The primary responsibility of a genetic consultant is to facilitate independent decision-making in situations for which there may not be a positive outcome (Owens et al., 2019). The genetic consultant should be able to provide answers to all questions that arise and provide information about support groups and other resources necessary for the patient.
A practical option would be to provide Mrs. Falls with reliable websites and brochures containing information about Edwards syndrome. To avoid an adverse reaction from Mrs. Falls, the author of this paper will help her understand medical terms and facts. Also, the author of this paper will explain to the patient the essence of the diagnosis and methods of treatment or relief of the condition in detail. All this will be carried out by taking into account this patient’s ethnic, cultural, and religious characteristics.
Proposal for Discussion Points
While consulting Mrs. Falls, the author would like to make sure that the following topics are covered in connection with Edwards syndrome: health, prevention, screening, diagnosis, prognosis, choice of treatment method, and monitoring of treatment effectiveness. Edwards syndrome affects health in the following way: this disease causes partial or complete trisomy on the 18th autosome, as well as multiple malformations (Hoon et al., 2018). Edwards syndrome is characterized by the following signs: anomalies of the musculoskeletal, cardiovascular, digestive, and genitourinary systems. Children with Edwards syndrome often have cleft upper lip and palate, ptosis, exophthalmos, strabismus, and a short neck with an excessive skin fold.
Prevention of Edwards syndrome is reduced to the careful planning of the upcoming pregnancy. It is required to study the couple’s family history in detail, identify risk factors, and conduct a genetic analysis. Genetic analysis is necessary to detect defective genes in the DNA molecule. The more mutations are detected, the higher the probability of having a sick child (Hoon et al., 2018). The only diagnosis of Edwards syndrome is prenatal screening, which is offered to every woman. Prenatal diagnostics is performed at the period of 11-13th weeks of pregnancy and includes ultrasound diagnostics of the fetus and biochemical screening.
Edwards syndrome is a chromosomal disease, so it is based not on a mutation of a particular gene but a defect of the entire chromosome, that is, a whole DNA molecule, namely, an additional chromosome. Unfortunately, the exact causes of Edwards syndrome have not been established. Such a violation is provoked by parents over 40 years old, the presence of such chromosomal disorders in the family of one of the child’s parents, etc. Treatment of Edwards syndrome is impossible since the chromosomal abnormality affects all fetuses or the born child cells. Monitoring the effectiveness of treatment, as a rule, is reduced to providing symptomatic care aimed at maintaining physiological functions, prolonging life, and improving its quality.
Genetic counseling is a necessary medical procedure that can help a patient plan a family, choose a life partner and prevent possible genetic abnormalities in children. The genetic consultant has a great responsibility because it is vital to calm the patient and help him cope with negative emotions. It is necessary to collect as much information as possible about diseases in the patient’s family, as this will significantly facilitate the doctor’s task. A timely genetic examination can influence the patient’s decision regarding pregnancy and starting a family. The consultant also needs tolerance, intelligence, good manners, compassion, and high empathy skills.
References
Abacan, M., Alsubaie, L., Barlow-Stewart, K., Caanen, B., Cordier, C., Courtney, E.,… & Wicklund, C. (2019). The global state of the genetic counseling profession. European Journal of Human Genetics, 27(2), 183-197. Web.
Ginsburg, G. S., Wu, R. R., & Orlando, L. A. (2019). Family health history: underused for actionable risk assessment. The Lancet, 394(10198), 596-603. Web.
Owens, D. K., Davidson, K. W., Krist, A. H., Barry, M. J., Cabana, M., Caughey, A. B.,… & US Preventive Services Task Force. (2019). Risk assessment, genetic counseling, and genetic testing for BRCA-related cancer: US Preventive Services Task Force recommendation statement. Jama, 322(7), 652-665.
Cells of human beings and other organisms contain genes that regulate all cells’ chemical reactions, making the cell to function and grow. In human beings DNA containing specific traits is passed on to generations through inheritance. However, currently, there has been two closely related technologies involved in altering the genetic materials, gene therapy and genetic enhancement (“The Moral Choices on CRISPR Babies.’’). Gene therapy involves altering genes to correct genetic defects and promote the prevention and curing of genetic diseases. On the other hand, genetic enhancement targets modifying the genes to augment the aptitudes of an organism outside the ordinary. These modifications of genes have been possible with the invention of technologies such as CRISPR that allow editing of the genes (Schapitl). Therefore, therapeutic use refers to process of bringing up genetic materials to the level of adequate performance, capacity, and health while enhancement entails taking genetic materials up beyond normal existing level of performance, capacity, and health.
Somatic gene editing impacts the cells of an individual under treatment and it is inherited to future progeny, making it difficult to predict. Somatic gene editing entails modification of the DNA of a person to allow treatment or curing of illnesses triggered by a genetic mutation (Doudna). In this method, CRISPR-Cas9 is employed to correct the genetic mutation and infuse modified cells back into the patient body to produce superior cells.
Germline genome editing refers to the alteration of the human embryo genome at its original phases, causing an effect on each cell of the body. Thus, it is asserted that the method requires substantial restrictions on usage to avoid causing harm to the generations. Germline editing is essential as it can help researchers ascertain an individual’s health benefits (Schapitl). Gene editing can produce healthy kids where there is recessive genes associated with a disease or a heritable genetic disorder. However, ethical questions have been raised as to whether the process is safe and effective for the use (“The CRISPR-baby scandal: what’s next for human gene-editing”). The technology can be done due to reproductive autonomy, whereby it asserts that human beings have the right to do whatever they want to get a baby of their preference without any limitations whatsoever.
The process of germline editing is likely to cause potential risks such as when incorrect genes are aimed causing modification of wrong trait can negative impact an offspring. There is also risk of off-targeting whereby when after fixing the problem, another one is likely to arise. Besides the safety concerns, implementation of these new gene-editing technologies has had issues in bioethics, which has caused its delay (“The Moral Choices on CRISPR Babies”). However, families with children who suffer from devastating genetic illnesses regard this technology as a means of getting rid of the mutation problem. According to Doudna, it has been challenging to conclude between diseases treatment and enhancement. It is depicted that using genetic editing is risky, and it is more probable to produce damaged children.
Furthermore, human beings have a linked genome system, and adding or subtracting a part affects the remaining part. Using CRISPR to edit genes can present collateral damages through off-target impacts that might not express show on the spot but show up years later or in another group in the progeny of the potential embryo (Doudna). Therefore, if the embryo with altered genome results in bad outcomes, an individual or government will be tasked with caring for the child for the entire life. As a result, society experiences costs and risks that outweigh the potential benefits for enhanced kids (“The Moral Choices on CRISPR Babies’’). Societal issues are likely to occur whereby if the embryo developed can have improved memory, it will create elites who only the wealthy families can afford.
Works Cited
“The CRISPR-baby scandal: what’s next for human gene-editing” Web.
“The Moral Choices on CRISPR Babies” Web.
Doudna, Jennifer. “How CRISPR lets us edit our DNA” Web.
Schapitl, Lexie. “Our Genes Affect Everything from Height to Heart Disease. What Happens When We Can Edit Them?” Vox, Web.
In some cases, changing the DNA of an unborn person is the same as changing fate and giving a chance for a happy future. Since science does not stand still, people have learned to influence DNA to a certain extent. To date, the idea of “designer babies,” which claims that it is possible to alter the genes of the embryo, carrying out specific genetic manipulations, is becoming pretty popular but needs to be explored more.
The opportunity to alter DNA is an excellent step toward the development of science, but it should be used carefully. While nature “has a marvelous mechanism to ensure that each human life has an identical number of chromosomes” and is unique, genetic changes should be utilized only in urgent situations (Belsky, 2015, p. 38). Genetic manipulations are a good idea for two profound reasons: a child’s abnormality or disease. The bioethicist Kevin Smith claims: “if several disorders could be avoided or delayed by genetically modifying humans, the average disease-free lifespan could be substantially extended” (as cited in Guy, 2019, para. 9). Other factors, such as parents’ wish to have a blue-eyed child or a boy instead of a girl, have ethical implications: those manipulations are intervention into the lives of minors and can damage the embryo. The altering DNA for such reasons should hardly be admissible. Therefore, a significant gap lies between the desire to choose the child’s sex or eye color and the striving to save the life or prevent the disease.
The idea of “designer babies” can hardly be evaluated as exclusively positive or negative. On the one hand, it indicates the development of genetics and contributes to the destruction of some diseases a child could suffer. On the other hand, the idea of designing unborn humans in the same way that technologists create computer machines seems unnatural. Therefore, in several cases, the manipulations with genes are indispensable and can bring extraordinary benefit, but in other situations, perhaps it would be better to entrust this matter to nature.
References
Belsky, J. (2015). Experiencing the lifespan (4th ed.). Worth Publishers.
Guy, J. (2019). ‘Designer babies’ could be just two years away, expert claims. CNN International. Web.
Variations in gene composition in any population are what cause evolution. However, the Hardy-Weinberg Law provides some conditions which when fulfilled, genetic changes will not occur in any sexually reproducing population. Genetic variations therefore occur when these conditions are violated. According to Hardy and Weinberg, a stable population can only be maintained if the following conditions are met failure to which variations would occur.
The first condition is for the alleles to be stable a condition which allows zero net mutation (for a zero net mutation to occur, the rate of forward mutation must equal that of the backward mutation). This condition is violated when the rate of forward mutation is not counteracted by the backward mutation rate resulting to net mutation which contributes to genetic variations and evolution.
The second condition is neutrality of the alleles towards each other such that they are all passed from one generation to another in the same proportion with similar abilities to survive and reproduce in any particular environment. Violation of this condition involves natural selection where one of the alleles adapt better than the other alleles thus possessing the advantages of reproducing and passing its copies to offspring over the other alleles.
The third condition is the effective closure of a population where no individuals leave a particular population or enter a new one. When this condition is violated, the population is opened allowing individuals to move from one population to another hence creating a net flow of genes which results to genetic variations and consequently, to evolution. The fourth condition requires the population to be large enough since it is based on statistics. This is because large populations are less subjected to deviations from the expected sampling. This condition is violated when a certain population is small to allow deviations from the normal frequency of reproducing parental genes.
These deviations resulting from errors in sampling are referred to as genetic drift and are contributing factors to genetic variations. This condition further maintains that fusion if gametes occur randomly according to the frequency of the genotypes available, a condition known as panmixis. In addition, genetic drift may result due to death or meeting of different genotypes by chance (Okasha, 2006, p. 1).
Genetic inheritance on behavior
All animals including human beings have in-built forces which enable them behave in a certain manner. Genes play an important role in determining an individual’s behavior. Though not directly involved, genes govern the development and functioning of the nervous system which in turn causes and controls the way than an individual behaves. Genes contribute only a little towards an animal’s behavior as environmental factors are the most determinant factors.
Different environments provide the opportunity for individuals to behave in a certain manner to the point of adapting that particular behavior. These adaptive characteristics may even e passed on to other generations. The behavior of the off spring will therefore be determined by the traits inherited from the parents. Some of the most common behaviors that are inherited include specific cognitive abilities which determine an individual’s ability to perform academically. Genetic research on animal and human behavior shows that genetic influence involves not only some few major genes but multiple of genes.
It is also possible that certain families have unique genes that are responsible for some behaviors especially health disorders such as the Huntington’s disorder. Behavior development is, in most cases, disrupted by few or minor genes such that their effects cannot be striking in a few individuals (Plomin, 2000, p. 1).
Caenorhabditis elegans as a model organism
C. elegans has been used to study the different functions of genes as well as mutations that cause diseases in man. Its gene structure has been used by researchers to identify and locate genes and mutations in the human genome to help understand many of the human disorders. For instance, C. elegans has long been used to study a genetic human condition of the kidney, the polycystic kidney disease, which involves growth of sacs in the human kidney filled with fluid. C. elegans has been used as a model organism to identify the pathways that lead to the growth of the cysts as well as understanding the protein mutations that result to development of the disease (Adams, 2008, p. 1).
Other animal models besides Caenorhabditis elegans include: Drosophila melanogaster, a fruit fly which is easily cultivated in the lab. Used commonly because it can be easily mutated and they grow fast allowing rapid generations. It is also large enough to see many of its body parts with the naked eyes. Another most used animal is Arbacia puntualata, a sea urchin used to study embryology. Hydra has been used to study regeneration and differentiation in animals as well as body symmetry. Besides vertebrates, invertebrates have also been used as model animals such as the Guinea pig, dogs and even cats among many others.
Developmental biologists have over the past decades used the nematode, Caenorhabditis elegans as a model animal to study the biological development of a cell. It has been the most preferred model organism/animal over the others because it has certain advantages that make the study work a lot easier and efficient. To start with, it is very transparent allowing the scientists to easily observe the cell that they are studying using a simple dissecting microscope.
It is also advantageous in that it has a small body which makes it easy to grow in large numbers in a cell culture. Its short life cycle of approximately three days allows scientists to produce as many generations as they desire for their studies. Breeding of the nematode is easy since it has both male and hermaphrodite sexes which means that males can mate with the hermaphrodites or in the absence of the males, the hermaphrodite can self-fertilize hence fertilization is always ensured. Advanced microscopes and other study tools such as antibodies can be used on the nematode. Its efficiency is added by the fact that it has a genome which has been sequenced making it much easier for scientists to identify the specific gene of interest (Brenner, 2010, p. 1).
Disadvantages of C. elegans
Besides being advantageous in scientific research, C. elegans has some disadvantages over the other model organisms. For instance, its small body is a disadvantage on the part of the animal in that it can easily be preyed on by other larger organisms. Similarly, its short life cycle may be a disadvantage when many of the nematodes die before breeding something which when repeated may deplete the nematode’s generation. Since many of the nematodes are hermaphrodites with only a few males, variations are not likely to occur because of self fertilization. As a result, certain genetic diseases will keep on being passed from generation to generation due to lack of gene varieties (Johnson, 2011, p. 1).
The purpose of this essay is to integrate genetic information in the Trosack case to ensure that the patients can deal with the genetic basis of the disease in their child. The appropriate members who can be included in an interdisciplinary team to gain more information on Trosack’s case include Dr. Zimmerly, Rita Trosack’s physician, Rita’s father, and Peter’s father. Dr. Zimmerly is suitable for the interdisciplinary team as he has the relevant knowledge and expertise to deal with advanced cases of maternity.
He is also well informed on Rita Trosack’s case as he organized for her chorionic villus sampling (CVS) test which would determine whether the baby has a genetic disorder. Dr. Zimmerly is also a suitable candidate for the interdisciplinary committee as he has prescribed prenatal vitamins for Rita which she is taking to manage her pregnancy until her due date.
The physician has also provided Rita and Peter with nutritional information and exercise which she can do during her pregnancy. He has also informed a couple of the basic warning signs that might signal any health problems to both of them. Rita’s father will be a suitable candidate for the study because his parents had two sons one of whom died at an early age of unknown causes. Rita’s father will be able to provide important historical information based on what his parents told him of his brother’s death. The circumstances surrounding the death will be important in determining whether the boy died of genetic circumstances or other causes.
Peter’s father will also be a suitable candidate for information as his parents had three children including him; two of whom (a boy and a girl) died of unknown causes. These unknown causal factors might be assessed by the team to determine whether they are genetically caused or there are other contributory factors to their deaths. These three people will be important in providing genetic information to determine whether Rita and Peter Trosack have the Tay-Sachs gene.
The type of information that will be collected from the three individuals will include family histories and evidence of whether the family has an autosomal gene that causes Tay-Sachs, medical information that exists on the deaths of the three children, whether Rita and Peter are Tay-Sachs carriers and how long the disease takes to materialize in the body of the carrier.
Once the people who will be involved in the interdisciplinary team for Trosack’s case have been identified and the relevant information has been collected from the three candidates, the next stage will involve a genetic diagnosis of the disease in both parents of the child. Tay-Sachs is a recessive genetic disorder that causes a relentless deterioration in the mental and physical ability of the sufferer. The disease is caused by a mutation in a single gene carried by the parents which are caused by large amounts of gangliosides that accumulate within the nerve cells of the body. These gangliosides eventually lead to the death of these cells causing cognitive, motor, and speech difficulties in the child as their mental and physical abilities continue to deteriorate as the disease progresses (Moe & Benke, 2005).
The genetics aspect of the disease has established that Tay-Sachs is a genetic disorder caused by a recessive autosomal gene where parents who have the disease-causing gene increase the chances of having a child with Tay-Sachs. Autosomal genes exist in every human being and any mutations that exist in this gene are passed on to the child. To determine whether parents are carrying a mutation in the autosomal gene, the Mendelian ratio is used to determine whether there is a 25% chance of the child suffering from Tay-Sachs. In the genetic diagnosis of the disease, physicians normally use an ophthalmoscope to detect the presence of macula which is a common symptom of the disease (Moe & Benke, 2005).
The macula is characterized by a red spot in the retinal area of the eye which occurs because of the accumulation of gangliosides in the sufferer’s brain. The red spot is the only normal part of the retina that can be observed by ophthalmologists to determine whether a child suffers from Tay-Sachs. Other techniques that can be used in the genetic diagnosis of the disease include microscopic analysis of the body’s neural network and molecular diagnostic techniques that analyze autosomal genes in the carrier’s body (Neudorfer et al, 2005).
Therefore, to evaluate the disease in the case of the Trosack’s, a complete physical examination of both Rita and Peter will need to be conducted through the Mendelian Ratio after which a detailed history of symptoms and hereditary disorders will be gained from any information provided by Rita’s father and Peter’s father. Another technique that can be used to determine whether the Trosack’s are carriers of the Tay-Sachs gene includes conducting a blood test which will measure the amount of hexosaminidase A (Hex A) activity in their blood (Moe & Benke, 2005).
The medical treatment of Tay-Sachs is usually directed towards supporting and comforting patients suffering from the disease as there is no cure. The goal of Tay-Sachs medication is to make patients as comfortable as possible as they progress through the various stages of the disease. One type of treatment that can be used to treat the disorder in young children involves providing respiratory therapy which is meant to deal with the accumulation of mucus in the child’s lungs. Chest physiotherapy (CPT) is usually used to reduce the amount of mucus in the lungs making it easy for people suffering from the disorder to breathe.
During the progressive stages of the disease, eating or swallowing becomes a major problem for most children who suffer from respiratory problems. To assist in the swallowing of food, feeding devices such as nasogastric tubes and percutaneous esophagi tubes are used to place food directly in the abdomen of the affected child. Another treatment option that can be used to treat children with Tay-Sachs includes the use of medications that control pain, seizures, and muscle spasms in Tay-Sachs patients (Walker, 2009).
The most common technique of dealing with Tay-Sachs is the prevention of the disease which is only possible by conducting screening or prognosis. The types of screening that are usually done to determine whether the parents of the child are carriers of Tay-Sachs include carrier testing and prenatal testing. Carrier testing is usually performed on couples from high-risk populations who are aware of the existence of a genetic disease or disorder from either their ancestors or their living relatives (Walker, 2009). In the case of Rita and Peter carrier testing is a suitable option given that they have limited information of whether their parents or ancestors have the Tay-Sachs gene.
Prenatal screening tests are most suitable for couples who have information on their family history and the genetic mutations that might exist in the family which might eventually lead to Tay-Sachs. This form of screening is usually performed when both parents cannot be ruled out for being carriers of Tay-Sachs genes. Some cases of prenatal testing usually find either of the parents becoming aware of their status which enables the physician to rule out the possible carriers of the disease. The most commonly used methods in the prenatal screening of the disorder are the enzyme assay techniques which detect the level of activities in the HEX A (hexosaminidase) enzyme within the body as well as conducting a chorionic villus sampling (CVS) procedure (Walker, 2009).
When prenatal screening is conducted with genetic testing, the possibility of determining whether the child has Tay-Sachs is usually high. Parents are faced with the choice of terminating the pregnancy (abortion) or giving birth to a child that will suffer from Tay-Sachs (Jameson, 1998). This decision is complicated further as there is no cure or treatment for the disease. The only assistance that children suffering from the disorder can be able to receive is medication and therapy that will ease the symptoms of the disease. Support groups begin to play an important part in helping Tay-Sachs parents deal with the effects of the disease on their children.
For Rita and Peter Trosack’s case, a support group that includes parents who have children suffering from Tay-Sachs would be important in helping them to deal with the feelings of denial, guilt, and anger especially now that they have decided to proceed with the pregnancy because of their religious and personal convictions. Support groups for Tay-Sachs will provide much-needed support to the two parents so that they can be able to accept the situation and also know how to deal with their child once he/she is born.
Parents with children suffering from Tay-Sachs are the best placed to provide guidance and support on how to manage the symptoms of the disease. Rita and Peter should therefore join a support group to enable them to prepare for the birth of their child. The pregnancy information that Dr. Zimmerly should provide the Trosack’s with includes the management of the pregnancy during the remaining months, what to expect during the pregnancy, how to prepare for the birth of their child, what nutritional foods Rita needs to eat as well as medication to manage the health of the child as well as birthing techniques that will minimize any further deterioration of the child’s health.
The ethical implications that exist on genetic information to determine whether the child suffers from Tay-Sachs include the risk of terminating the pregnancy, the risk of carrying the pregnancy to term, and the risk of terminating or carrying the pregnancy without sufficient genetic information.
The first ethical implication of terminating the pregnancy is usually based on the amount of genetic information that has been presented to the parents with regards to whether they are carriers of the disease or not. While terminating the pregnancy might seem to be the easiest option, it is usually difficult for most parents and individuals who value life no matter how small it is. The ethical implication in such a case, therefore, becomes availing genetic information that will more than likely increase the risk of terminating the pregnancy (Jameson, 1998).
The second ethical implication bears a lot of psychological, emotional, and financial burden to the parents once they decide to carry the pregnancy to term. Managing the symptoms of the disease will prove to be an uphill task for both parents given that the disease immobilizes the child and causes them to have seizures which affect their cognitive abilities. Raising a child with psychological impairments might prove to be psychologically damaging to the parents especially during the advanced stages of the disease. The ethical implication of availing genetic information in such a situation influences the decision of parents who do not want to terminate the pregnancy.
In the third option, insufficiency of genetic information might affect the outcome of parents who have decided to either raise or abort their child. In some cases, if one parent is a carrier, they might decide to terminate the pregnancy regardless of whether the other parent is a couple or not. This might prove to be a harmful decision when conclusive tests reveal that the child does not have the disorder. The availability of genetic information, therefore, has ethical an implication on whether the parents of the child will go through or terminate the pregnancy. Genetic information forms the framework for Tay-Sachs and pregnancy information which will be vital in making the overall decision with regards to the pregnancy (Jameson, 1998).
Rita and Peter have both decided to keep the baby as they have strong religious and personal beliefs which have made it difficult for them to consider abortion as an option. Their decision means that they will carry the pregnancy to term after which they will manage the symptoms of the disease as it continues to progress to the more advanced stages until the child eventually succumbs to the illness. Rita and Peter’s decision to raise the child will be psychologically traumatizing to them as they will get to raise the child for the first three to four years of their life. Their decision is mostly based on the emotional need to raise a child given that they have been trying to conceive for two years.
While the easier option would be to abort or terminate the pregnancy, the overall need to bring life into the world as well as their personal and religious beliefs has formed the overall basis of Trosack’s decision. Despite the limited amount of time the couple will have their child given that the disease kills infants during their early childhood, they will at least have given the child a lease of life no matter how limited it is. Medical practitioners and physicians see the option of termination to be an easier outcome because there is no cure for the disease. The overall decision however lies with the parents of the affected child.
As the case manager for the Trosack’s as well as a high-risk obstetric nurse, the most practical solution would be to terminate the pregnancy as the health of the child will gradually deteriorate with the progressive destruction of the central nervous system leading to cognitive, mental, and physical problems. The impact of the disorder on the child might cause them to suffer from paralysis, blindness, and a lack of motor abilities making it difficult for the child to move. With such options and the lack of a cure, the most viable alternative becomes to discontinue the pregnancy. While screening programs such as the CVS have reduced the incidence of the disease, termination of the pregnancy has been identified as the most suitable solution (Tulchinsky & Varavikova, 2009).
In considering Rita and Peter’s decision to keep the pregnancy, the case manager has to place the couple’s interests first before any medical knowledge that they might have on how to manage the disease. This will require exercising beneficence where the health and welfare of the Trosacks will be taken into consideration by the doctors and physicians concerned with their case. The case manager, therefore, has to advocate for the couple’s decision to Dr. Zimmerly and other physicians involved in Trosack’s case to make them understand that the couple intends to carry the pregnancy to term as well as raise the child. However, Rita and Peter’s decision will be plagued with both ethical and legal considerations where ethically they will raise a child that has a disorder that lacks any curative therapy (Jameson, 1998).
The ethical considerations for such a decision will affect the couple where they will be unable to reduce the pain and suffering of their child which can only be achieved by reducing the incidence of the disorder and terminating the pregnancy. The legal considerations that will arise as a result of their decision will mostly increase their liability to health risks once more screening tests are performed during the pregnancy. Such tests might further exacerbate the health of the child as well as that of the mother as they await the due date. Legal considerations will therefore arise when offering screening without any established methods of counseling, education, and communication which might inappropriately influence the moral decision of the parents (Jameson, 1998).
References
Jameson, J.L., (1998). Principles of molecular medicine. New Jersey: Humana Press.
Moe, P.G., & Benke, T.A., (2005). Neurologic and muscular disorders: current pediatric diagnosis and treatment. New York: McGraw Hill.
It is puzzling that monozygotic twins who originate from a single egg and share similar appearances often grow to depict slight differences irrespective of the genes showing a considerable genetic component. The idea of epigenetics can better elucidate this conundrum. Epigenetics refers to the study of how cells regulate gene functions and activities without altering the essential sequence of DNA (Hanson & Hotaling, 2020). The model helps in understanding how variations linked to DNA control how genes are switched off or on. These modifications are anchored in DNA and do not transform the building blocks of this hereditary material.
The PBS video provides insightful discussion about this perplexing notion by offering a detailed explanation of identical twins and the commencement of diseases. The documentary shows that epigenetic variations mark as consistent and natural happening but can be impacted by other elements such as environment, age, disease state, and lifestyle. Epigenetic changes often occur through cell regeneration into brain cells, liver cells, or skin cells. Through this process, the cell adjustments can result in more harmful ramifications, such as the commencement of diseases like cancer and even other conditions such as obesity (Hanson & Hotaling, 2020). The movie also reveals three common systems that are linked to gene silencing and are highly regarded in the start and sustaining of epigenetic changes. The three entail non-coding RNA, histone modification, and DNA methylation.
Epigenetics Article
In their article, Hanson and Hotaling (2020) clarify how epigenetic deviations are involved in regulating many processes in the human body. For example, the concept serves a role in controlling the male reproductive system. In the article, epigenetics is described as modifications to an individual’s phenotype, which emanates distinctly and separately from the fundamental DNA sequence. The two main molecular alterations within this realm of epigenetics are posttranslational histone amendment and DNA methylation.
The authors further offer a vivid demonstration that explains how epigenetics partly contributes to infertility among men. For example, they highlight that different epigenetic outlines in semen that have been identified in males include low sperm count, poor movement of sperm, and abnormal semen shape. Reconfigured pathways of epigenesist, which effectively build high qualities semen, encompass lifestyle watch and environmental factors. Furthermore, epigenetics’s irregularities might have damaging consequences on semen assessment parameters, placentation, implantation, fertilization, or embryonic growth (Hanson & Hotaling, 2020). While epigenetic adjustments do not trigger alterations within the gene, it could offer a reasonable clarification to some occurrences of men impotence were no genomic inconsistencies through the known conventional methods. Besides changes in the gametes, epigenetic differences which change the spermatozoa could affect postejaculatory semen and their survival could cause disturbances to typical cytokine instruction liable for primary embryogenesis.
Family History
After completing my family history based on Dr. Oz’s Work Sheet, it is now clear how the concept of epigenesis works. While several differences exist among the diseases identified in the family members, the history marks a critical risk factor for various conditions, as seen in the commencement of illnesses among the family. For example, the outcome of the score shows that many of my family members have anemia, high cholesterol, asthma, and allergies. Reflecting on the model of epigenetics, it is clear that every member of my family inherited some genes, encompassing socioeconomic and cultural experiences that positioned them at danger of some of these diseases.
Certain conditions, such as human cancer, develop as a result of increased accrual of epigenetic shifts. The changes are recognized to show in both normal and cancerous cells. Precise trends of changes are connected to ecological influences. The build-up is related to the threat of cancer and can be used for cancer risk evaluation. Moreover, Takeshima and Ushijima (2019) highlight that a risk metric based on hereditary genes is not enough because it fails to encompass environmental involvement and age factors. Based on the completed family history assessment, I would not wholly link my risk metric to the outcome of the investigation and infer that I am vulnerable to the above-identified conditions. However, considering inherited genetic modifications identified from the parents, siblings, and other close relatives, I would conclude that environmental interaction and susceptible genomes are directly interrelated to the pathogenesis of such ailments.
Discussion
After finishing the 100 Living questionnaires, the outcomes were slightly fair, even though I anticipated much better scores. Explicitly, my healthy life expectancy stands at about 65 years. The outcome could be partly attributed to my lack of a consistent and healthy diet and lifestyle. Alternatively, my complete life expectancy score is 76.7 years which stands for the years without cancer, diabetes, or heart disease. My overall life expectancy score could be impacted by family history, demographic factors, lifestyle, or environmental factors. Further, my possible life expectancy stands at 96.5 years based on the conducted assessment, thereby exposing that I can hypothetically add about 22 years with a huge lifestyle amendment and sickness prevention strategies.
While it is hard to locate the exact factor that impacts these outcomes, I would cite economic well-being, socioeconomic status, and health behaviors among the main facets behind the outcome. Socioeconomic conditions can impact the health results of a person since it is directly associated with the value of healthcare that an individual can access (McCrory et al., 2019). Furthermore, economic welfare has a huge capability to influence the outcome since it can facilitate access to healthy meal plans and lower anxiety and stress. Finally, healthy conduct impacted the outcome due to my inconsistent exercise pattern and poor diet.
Enhancing Life and Longevity
The concept of epigenetics remains perplexing on how it leads to differences even between identical twins. However, with the vast knowledge acquired through learning this concept coupled with the discerning exercise of assessing family history, I commit to improving my longevity and health by making numerous adjustments. Part of the changes could include adopting a healthy diet that integrates fruits, vegetables, and whole grains. Whole grains help to lower the danger associated with diabetes and heart disease since they have endosperm, germ, bran, and kernel.
Alternatively, fruits and vegetables are brilliant sources of minerals, vitamins, nutrients, and enzymes. The approach would go a long way in reducing the chances of developing heart-related conditions. Furthermore, I will start regular exercise to ensure that I remain active and decrease the risk of heart disease, hypertension, and diabetes. Finally, by exercising regularly, I would lower anxiety and stress linked to frustrations over issues at school, home, and the workplace. Therefore, these minor changes would result in adjustments in my behavior and mindset thereby impacting how my offspring handle stressful issues.
One of the assumptions of molecular biology from an evolutionary perspective is that the triplet nature of the genetic code is a traditional form of two-nucleotide coding. In other words, it is assumed that protein coding using three nucleotides is an evolutionary modification of coding based on two nucleotides. In this sense, one might expect that the mRNA UUU codon, which encodes the formation of the amino acid Phenylalanine, might have been previously represented by the two-nucleotide UU codon encoding the same amino acid. In fact, such speculation makes sense, and the following paragraphs aim to use compelling biological evidence for this thesis.
It is now well known that DNA consists of four nucleotides (A, T, G, and CD), and every three variations of these nucleotides create a particular amino acid. In this regard, there is the Central Dogma of Molecular Biology, which determines that DNA through transcription gives rise to mRNA, which through translation is converted into the amino acid sequence of a polypeptide. According to the law of mathematics, coding four elements into three sites could yield 43 variants or 64 combinations of nucleotides. If only two nucleotides were enough for coding, with no change in the number of monomers forming the DNA, this would result in 42 variants or only 16, which is exactly four times less.
In this sense, the first intuitive argument is that the diversity of protein molecules used to be significantly lower and their amino acid composition scarcer. Chemical evolution continues to add to the number of emerging substances, but earlier, when life was just beginning, it is highly likely that the three-nucleotide code was redundant. Cells did not expend as much energy to use triplets because protein molecules were meaningfully simpler.
In addition, the genetic code is degenerate, which means that the same amino acid is encoded by several codons at once. For example, a study of the mRNA table makes it clear that lysine is encoded by two triplets at once (AAA and AAG) and serine by six (AGU, AGC, UCA, UCG, UCU, UCC). In fact, almost all functional amino acids, except for Methionine, Tryptophan, are encoded by at least two codons. It can be seen that the first and second nucleotide are always the primary fixatives, while the quality of the third nucleotide in the codon can vary. This leads to the idea that two nucleotides are historically more fundamental.
At the same time, the effect of frameshift on the posttranslational outcome has been investigated. In particular, it is estimated that deletion or alteration of the first or second nucleotide in a codon always resulted in an inability to create a protein (Hardison, 2021). Alternatively, changing the third nucleotide only affected the final quality of the amino acid but still led to its formation. From this, one can conclude that the nucleotide was initially based on the use of two nucleotides, but over time, biochemical evolution led to the importance of the third.
The first phase of the PCR technique involves the most intense heating of the DNA strand, causing the hydrogen bonds that form the complementary helical complex to break down. Thus, the helix is converted into a mixture of two linear stranded nucleotide chains simultaneously in solution. It is noteworthy that the nucleotide composition of the mixture does not differ in this case because no qualitative changes in the molecule, except for the breaking of the bond between the nucleotides, occurred. In other words, if the initial DNA sample had a GC composition equal to 70%, then the amount of guanine and cytosine in the already unpaired DNA strands will remain unchanged even after the whole molecule is destroyed.
In the experiment under consideration, it is proposed to use two samples of DNA, one of which contains 70% of GC and the other containing only 45%. At this point, one can conclude that the two molecules are not related since the composition of close biological genera and, even more so, the species of GC is very similar (Machado, & Gram, 2017). An essential feature of using guanine and cytosine specifically for this characteristic of any nucleotide chain is the presence of three hydrogen bonds between the C and G pair. As it is known from the kinetics of chemical reactions, a more significant number of bonds usually requires more input energy to break them. In other words, a DNA molecule with 70% GC is more resistant to degradation and denaturation, which means that more effort is required to break it.
A reasonable conclusion can then be drawn that DNA with 70% GC will require higher temperatures to break the entire molecule, in contrast to DNA with almost 1.6 times lower proportion of G and CD nucleotides. In other words, the first DNA sample could be used at higher annealing phase temperatures, as opposed to the second sample, which would require less heat input. However, in either variant, temperatures as low as 100°C may be sufficient to separate the helix of the nucleotide chains.
References
Hardison, R. (2021). Genetic code. Libre Texts. Web.