Genetics V. The Environment And Their Effects On Development

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Genetics and the environment shape the development of an individual. This fact is embodied by the idea of nature versus nurture. Because both of these factors are interrelated, scientists have questioned which factor has more influence upon the various aspects of personal growth. The parts of development genetics and the environment can affect include physical and behavioral maturation.

A person’s physical development is strongly affected by their genes inherited from their parents. Parent’s genes predetermine the limits of an individual’s hight and other characteristics including the variability in eye color, hair color, body composition, and skin tone. When two parents are homogeneous for a brown eyed allele, they cannot have a blue eyed child, but if both parents are heterozygous and have a blue eye allele, there is a twenty-five percent chance that their child will inherit homozygous alleles that create a phenotype for blue eyes.

With physical attributes such as hight, parents’ genes dictate the range of hight their offspring can obtain. The variability in hight is a result of many external factors in the environment including nutrition and events during the child’s growth. While this is true, many of these qualities can be changed or are influenced by the environment. A person who inherits genes from their parents to be tall needs to have nourishment during their years of physical growth to reach their hight potential. People can change many of their physical attributes by choice. The action of choosing to change one’s characteristics is a result of the surrounding environment and its pressures. An example of this is when a person whose genetic make up causes them to have fair skin and brown hair decides to go to the tanning bed and dye their hair blonde. Culture, which is part of the environment, influences individuals to alter themselves in search of recognition from others. It is possible for people to change their phenotype with gene therapy.

A person’s outward appearance and internal structure are guided by their genes. Internal changes are a result of the environment influencing genetic tendencies. This fact illustrates the evolutionary concept of natural selection which suggests that only the strongest individuals in a population will pass on their genes to prosperity. In places where there is sun during most of the year, the population tends to have darker skin. This is a result of an increase in melatonin production which is a form of natural sun screen and is produced in the presence of sunlight.

Environmental affects can be seen within people who have sickle-cell anemia. This disease is hereditary and is a result a human population adapting to protecting the human race from malaria. This shows that environmental conditions can cause a hereditary change that protects a population by only allowing the individuals with the strongest genetic makeup to reproduce. A person who has homozygous alleles for sickle-cell anemia shows symptoms of the disease, but cannot experience the affects of malaria. However, an individual who is heterozygous for the alleles of the disease is not necessarily plagued with the symptoms and cannot develop malaria. Furthermore, a person who does not have the alleles coding for sickle-cell anemia is susceptible to contracting malaria, and thus, do not have genetic protection from this environmental factor. Other genetic diseases are different in their inheritance patterns.

While research is conducted on the theories of nature versus nurture and its physical manifestations, behavioral development has many genetic implications. Human beings are genetically predisposed to many personality traits ranging from developing alcoholism to enjoying licorice and football. Behavioral Genomics “is the study of the behavior effects of the genome” (88) and “focuses on the influence of genes on behavior” (87). Behavioral geneticists use studies based on identical twins separated at birth and raised in different environments to evaluate the extents of heredity influence upon a persons development. Through these studies, geneticist estimate the “heredity of intelligence, behavior, learning disorders, and personality traits” (87). These scientists have determined that although genes set the foundation for behavior, the environment shapes a person’s behavioral tendencies once they are born. “Genetics can affect behavior only indirectly and are moderated by environmental effects” (86) meaning that a person may be predisposed to behave a certain way, but a person’s surroundings directs the extent of their gene’s influence upon their behavior.

Whether a person becomes a drug addict is a result of the interaction between the environment and their genes. An individual who is genetically predisposed to become an alcoholic is much less likely to develop this disease in a culture where alcohol is taboo. A person who has the same genetic disposition and lives above a bar will develop alcoholism at a much higher rate. A genetic disposition is defined as “ an inherited tendency to be susceptible to or to develop” (270) with things varying from substance abuse to mental diseases such as schizophrenia. Studies have shown that certain racial groups have a higher incident of substance abuse. While alcoholism is not an inherited illness, but a genetic predisposition “certain factors related to the metabolism of alcohol are genetic” (270). The neurotransmitter, GABA, has been important in understanding the implications in alcoholism. While this may be true, the racial groups identified to have higher rates include African Americans and Latinos. It is difficult to determine if the studies’ results show a genetic tendency or are a result of environmental affects. Because many of these groups tend to live in poorer areas where substance abuse is more prevalent, the higher occurance maybe a result of environment which is an extraneous factor.

Genetics and the environment both play a crucial role in the development of an individual. The environment affects individual growth differently depending on genes, but both parts are needed to shape a person’s maturation. Because of this fact and the reality the interrelation of nature versus nurture, neither factor can be said to have more of an affect upon a development.





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