Lecture 6 Outline - Expressivity : the degree to which a...

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Bio 352 1 of 4 LECTURE 6 : Modifications to Mendelian Patterns Today’s topics: 1. Dominance 2. Penetrance 3. Multiple alleles 4. Gene interactions. Readings : Pierce, pgs. 99 – 117; 119 - 120 In Lecture 6 we are going to investigate patterns of inheritance vary from those predicted by Mendel’s 1 st and 2 nd Laws – these laws hold for many cases, but they are not sufficient to explain ALL patterns of inheritance. Dominance : heterozygote has the same phenotype as one of the homozygotes. Incomplete dominance – heterozygote phenotype is intermediate between the 2 homozygote phenotypes -- Figure 5.2 Codominance : heterozygote simultaneously expresses the phenotypes of both homozygotes -- heterozygote is not intermediate between homozygotes. Summary: Table 5.1 . Penetrance : % of individuals having a particular genotype that express the expected phenotype.
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Unformatted text preview: Expressivity : the degree to which a character is expressed. Example Polydactyly in humans Figure 5.3 Bio 352 2 of 4 Multiple alleles . Feather pattern in mallard ducks -- Figure 5.4 . ABO blood types Figure 5.5 . Gene interaction . Example : fruit color in the pepper, Capsicum annuum Figure 5.6 . Epistasis results in deviation from the normal 9:3:3:1 phenotypic ratio. The epistatic and the hypostatic gene. Bio 352 3 of 4 Recessive epistasis Example: coat color in Labrador Dominant epistasis . Example: Summer squash -- Figure 5.9 . Sex-influenced traits Figure 5.12 Bio 352 4 of 4 Sex-limited trait-- Figure 5.14 Cytoplasmic inheritance Genetic maternal effect Limnaea peregra ( Figure 5.17) Next Time : Pedigree Analysis (Lecture 7) Readings : Pierce, pgs. 134 - 142...
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This note was uploaded on 05/07/2011 for the course BIOLOGY 352 taught by Professor Townsend during the Spring '08 term at San Diego State.

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Lecture 6 Outline - Expressivity : the degree to which a...

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