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Unformatted text preview: Section 1 Evolution and Genetics I. Terms To Know Before we begin to talk about the role of genetics and inheritance in psychology it's important that we get a clear understanding of some of the terms which we will be using. There are some common misconceptions which should be avoided and we can avoid some of them by knowing the correct meanings of definitions of words that are often tossed around without a full understanding of what they mean.. A. Gene The definition of gene is one source of confusion because there are two acceptable definitions based on the context being discussed. While they are similar in meaning they are not exactly the same. A gene can be an observable inherited trait. Anything from how curly someone's hair is to their blood type or whether or not theyre double jointed. A gene can also mean a specific deoxyribonucleic acid (DNA) sequence which codes for a specific polypeptide or protein. Sometimes the things we see as a single observable trait may be coded for by more than one DNA sequence. Some DNA sequences may not result in an easily observable trait. B. Genotype The genotype is the DNA content of a cell's nucleus, whether a trait is externally observable or not. C. Phenotype The phenotype is the pattern of expression of the genotype or the magnitude or extent to which it is observably expressed. D. Monozygotic The term monozygotic means "derived from one fertilized egg." Identical twins are, therefore, monozygotic twins that share the exact same DNA just as they shared, essentially, the same uterine environment. E. Dizygotic The term dizygotic means "derived from two fertilized eggs." Fraternal twins are dizygotic twins and only share half the same DNA but , essentially, the same uterine environment. F. Clone Technically speaking, a clone is any organism that shares the same genotype with another. Monozygotic twins are clones. So are two garden plants taken from the same cutting. And so are two bacteria that have just resulted from the division of one bacterium. I I. Common Misconceptions There are still more misconceptions that should be addressed so that we can understand the role of genetics on behavior. A. One Gene means ... One common misconception arises from an old outdated simplification used in many biology classes: "One Gene = One Protein." Actually, some genes (DNA sequences) can yield more than one protein. For instance, one gene found in the brain for, proopiomelanocortin (POMC), yields 5 proteins once it has been fully processed. Additionally, most observable traits are polygenic (influenced by more than one gene) rather than controlled by a single gene....
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- Spring '07