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HMB265H1 (242)

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Human Biology
Stephen Wright

st LECTURE 13 March 1 Most variation is quantitative in nature, despite what was said in the first half of the course Quantitative genetics will be focus Phenotypic variation isnt always qualitative discrete traits: either blue or white, etc Complex traits AKA quantitative traits In general, two or more genes contribute to the overall phenotype AND the environment plays a larger role than in single traits Diabetes considered complex trait o Many genes responsible for the overall phenotype of the individual o Many genetic risk factors AND environment = diet, exercise, etc. plays large role on clinical phenotype seen Quantitative traits often show continuous variation kind of like a bell curve o Ex. height o In simple Mendelian genetics predictable ratios and inheritance patterns o With other traits, like diabetes and height, no predictable Mendelian ratios and complex inheritance patterns o Range of values thus complex or quantitative traits Continuous variation with almost infinite number of values or states Genetic basis exist? o Yes underlying genetic mechanisms are the same o Laws of segregation and independent assortment still apply But because were dealing with more than one gene at the same time and the effects of the environment predictable ratios not seen Thus continuous range of values Meristatic traits also quantitative in nature o Type of discrete trait not just two states o Still range of values but not a continuous range o Ex. number of children cannot have 2.5 kids o Still complex traits complex inheritance patterns Obscured because normally do not see Correspondence of one to one Complex traits dont have one to one ~Like in Mendelian traits Hence the uND~Erlying laws A~RE obscured Frequency of number of individuals displaying trait and the different traits on the x-axis But there are also other types of dominance relationships o For instance, incomplete dominance a blending o Intermediate phenotype
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