In each chromosome there are innumerable genes. Human Nature and Human Individuality.Dr. Cleveland - G E Correlations
So in PKU, a single gene can dramatically affect behavior: Oxford University Press, 1979. The hormonal secretion by these glands gives rise to another intracellular environment.
The chromosomes in our cells are not affected by any change that takes place within our body cells. Genetic mutations in the retina provide the strongest evidence that genes influence behavior, and while it is logical to assume that the same could be said for other mutations, there is no credible evidence to suggest that other mutations have the same effect on human behavior.
The fact that the two had been reared in very different circumstances, and hence had had very different experiences, was overlooked. Environment includes all the extrinsic forces, influences and conditions which affect the life, nature, behaviour, the growth, development and maturation of living organism Douglass and Holland.
They will observe that environment has an impact on genes expression.
Swanson, Carl R. Supporters of heredity say that the environment cannot change a dog into a goat. But they are wrong. The physical characteristics such as height, weight, colour of eye and skin, social and intellectual behaviour are determined by heredity.
The treatment for PKU illustrates the principle that the way a gene is expressed depends on the environment in which it is expressed. All the social factors stated above shape the personality of the child.
Fraser c. In simple terms environment means the society, the fields of society and even the whole world. This defective gene was no longer expressed in mental retardation, because the environment was different: However, we find more resemblances in identical twins because they are born out of monozygotic.
Fraternal twins also differ from each other, because they are born out of different genes. The home atmosphere, parental love and affection, association with sibling, neighbours, peers, teachers, etc. A clear, accurate, and readable book on medical genetics; hereditary disorders, genetic counseling, prenatal diagnosis, sex selection, twins, and more.
Genetic Concepts, Kit, Cat. Cebco Standard Pub.
Prentice Hall, 1980. In the same way, the effects of environment depend on the genes with which they work.
Lippincott Co. Judith Rich Harris.