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BIOLOGY 2C03 (138)
Joe Kim (16)
Lecture 4

Lecture 4 - February 4, 2013.docx

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Joe Kim

BIO 2C03 2013 Lecture 4February 4Quantitative and Qualitative GeneticsQualitative Characteristicsdiscontinuous characteristics exhibits only a few distinct phenotypes o May be determined by one gene with many alleles or multiple genes o Essential for outlining the rules of inheritanceMendel picked these traits to study that showed discontinuous traitso Phenotype tall or dwarf o Phenotype dwarf short medium tall very tallQuantitative Characteristicscontinuous characteristics continuous variation within a range of phenotypes o Many are polygenic o Often affected by variation in the environment even one gene can display this o Often both play a role multifactorial o Even one gene can produce a quantitative phenotype if it is determined by multiple alleles and if environment increases the range o Phenotype a quantitative measurement number such as 21 cm 225 cm 28 cmTypes of Quantitative TraitsContinuous Variationan assume any value between two values boundaries the number of phenotypes is limited by the resolution of the measurement tool o Eg Human height seed weight milk production Threshold Characteristicsnot continuous trait is simply present or absent but determined by multiple factors o Eg Human cancerpresent or absent but many contributing factors Polygenic Inheritance in Wheat NilssonEhledid the same sort of study as Mendel parental cross between two pure breeding lines o Looks like incomplete dominance if one gene is involved what ratio is expectedModified dihybrid ratio o Assign genes as if it were a dihybrid crosso Assign alleles as contributing or noncontributing like incomplete dominance at each geneA B contribute pigmentA B do not contribute pigment 1
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