Lecture 4 Bio325 Fall 07

Lecture 4 Bio325 Fall 07 - alleles of two or more genes...

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1 alleles of two or more genes required for the expression of one trait: Fig. 3.12 2 genes, 4 alleles, but only 2 phenotypic classes Two genes required for a single pathway can show: complementation precursor 1 precursor 2 product A B Fig. 3.17 precursor 1 precursor 2 product A B or
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2 epistasis : interactions between 2 genes such that the alleles of one gene mask the effects of the alleles of another gene example: coat color in labrador retrievers: the e allele masks the effects of the B and b alleles; therefore the e allele is epistatic to the B gene the e allele has to be homozygous to have this effect, thus this is an example of recessive epistasis Fig. 3.14 The two basic coat colors in Labrador Retrievers are black (BB or Bb) and chocolate (bb). However, for the black or chocolate to be expressed requires the presence of a dominant allele at the extension (E) locus. If the genotype at the extension locus is ee, the dog will be yellow regardless of its genotype at the B locus. The relationship between genotypes and phenotypes is as follows: B-E- = Black bbE- = Chocolate --ee = Yellow Example: (B - means that the second allele can be either B or b) 1. What is the genotype of a black labrador retriever if you know that his father had a black coat and his mother
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This note was uploaded on 06/19/2008 for the course BIO 325 taught by Professor Saxena during the Fall '08 term at University of Texas at Austin.

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Lecture 4 Bio325 Fall 07 - alleles of two or more genes...

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