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CA (650,000)
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HMB265H1 (300)
Lecture

Notes taken during lecture


Department
Human Biology
Course Code
HMB265H1
Professor
Stephen Wright

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LECTURE 13 March 1st
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
oMany genes responsible for the overall phenotype of the individual
oMany 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
oEx. height
oIn simple Mendelian genetics predictable ratios and inheritance
patterns
oWith other traits, like diabetes and height, no predictable Mendelian
ratios and complex inheritance patterns
oRange of values thus complex or quantitative traits
Continuous variation with almost infinite number of values or
states
Genetic basis exist?
oYes underlying genetic mechanisms are the same
oLaws 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
oType of discrete trait not just two states
oStill range of values but not a continuous range
oEx. number of children cannot have 2.5 kids
oStill 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
oFor instance, incomplete dominance a blending
oIntermediate phenotype
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