Exam 3: Seciton 1: Beginnings: Heredity and Environment

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Within hours after conception, a zygote begins duplication and division. First the 23 pairs of chromosomes carrying all the genes duplicate, forming two complete sets of the genome. These two sets move toward opposite sides of the zygote, and the single cell splits down the center, forming two cells. Each of these cells contains the original genetic code.
These two cells duplicate and divide again, becoming four, which duplicate and divide, becoming eight, and so on. At approximately the eight-cell stage, although duplication and division continue, differentiation begins. During differentiation, cells specialize, becoming heart, ear, or liver cells, etc.

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Nature and nurture can both contribute to a person experiencing alcoholism. In some individuals, genes (nature) can create the addictive desire to drink to excess. In addition, each human body metabolizes alcohol differently. Inherited personality traits may make alcoholism more likely, too.
The environment and social factors (nurture) are important because some environments (such as growing up with an alcoholic parent or being friends with an alcoholic) encourage a person's alcohol use.

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Epigenetics refers to the interaction between an individual's genes and the environment to determine the individual's phenotype. The environment can influence which genes get expressed in an individual's phenotype. If an individual inherits the genes associated with diabetes and then eats a poor diet or leads a sedentary lifestyle, the person will be apt to develop diabetes. Conversely, if the same person eats a good diet and leads a healthy lifestyle with plenty of exercise, he or she may prevent the expression of the diabetes gene.