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Lecture 10

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Biology (Sci)
BIOL 202
Mario Chevrette

Lecture 10 Quantitative Inheritance Penetrance = #showing phenotype/total of that genotype Expressivity refers to the degree to which an individual express the trait. The environment affects how phenotypes are expressed. The polygenic or continuously varying traits and the environment lead to a varying degrees of phenotypes in a population. The relative contribution of nature and nurture differs from environment to environment. Inheritability: the proportion of the variation of traits, and how the genes/environment causes variation among a population. E.g. 65% of variation for conservatism is caused by the genetic information, 35% caused by environment. Quantitative genetic variation is the basis for selective breeding, concentrating more and more towards a desired trait. While many evolutionary traits are seen to be continuous, Mendelian theory for 1 or 2 discrete genes are discrete. Edward M. East’s work on tobacco explained how the two could be combined to explain natural phenomena. East worked on the length of the tobacco flower, which varies among tobacco populations. He bred two inbred lines with different corolla (flower) lengths. The first generation of progeny has the same genetic makeup as each other, and has a distribution curve. The second generation of progeny has a much larger range of corolla length to choose from, this is due to the recessive genes becoming capable of being expressed. This shows that both genes and environment plays a part in the expression of the genotypes into phenotypes. Phenotypic distributions of different genotypes have means among them that
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