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Lecture 11

BIOL 207 (10/04/13) Lecture 11: Interaction Between Alleles of One Gene | Lecture 12: Sex Chromosomes

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University of Alberta
Biology (Biological Sciences)
Mike Harrington

BIOL 207 (October 4, 2013) Lecture 11: Interactions between Alleles of One Gene | Lecture 12: Sex Chromosomes  Purple flowers, in comparison to their white counterparts, have a P-gene that make an enzyme for purple pigment (anthrocyanin)  For pea plants, the round seeds have an A-gene that makes a starch-branching enzyme o Wrinkled peas are made because they do not produce this enzyme  The extra glucose makes the peas swell and then shrink to form wrinkles Pleiotropy  One gene influence many phenotypic expression Types of Allele Interaction  Incomplete Dominance o Intermediate phenotypes displayed in heterozygous offspring (Ex. In Flowers: Parents = red and white; offspring = pink)  In other words:  100% allele activity = red pigmented plant  50% allele activity = pink pigmented plant  0% allele activity = white (colourless) plant  Codominance o Heterozygotes display both parental phenotypes of a gene expression  Ex. Marbles cows  Roan and white patches  Lethal alleles o Heterozygous offspring exhibit a different phenotype than a pure-breeding dominant genotype BUT  If the offspring is homozygous for the recessive allele, it will die  Why? Because that allele prevents activity of an essential gene for living (organisms becomes non-viable) Variations on Mendel’s 3:1 Ratio Because of Above Allele Interactions (red/white example allelt combination)  Compl
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