BrookerChp4_ExtendedMendel - G Overdominance heterozygote...

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Chapter 4 – Extensions of Mendelian Inheritance I. Genetic conventions A. Mendelian convention for denoting alleles B. Drosophila convention for denoting alleles II. Different types of Mendelian inheritance [Table 4.1] A. Simple Mendel: dominant vs. recessive 1. Loss of function mutation 2. > 50% of a specific gene product may be enough [Fig. 4.1] 3. But, can you trust your eyes . . . Mendel did [Fig. 4.3] B. Lethal allele: essential vs. nonessential genes 1. Time of expression: embryonic vs. newborne vs. adult death (age of onset) 2. Conditional lethal alleles 3. “Semi-lethal” alleles C. Incomplete dominance 1. Intermediate phenotype [Fig. 4.2] D. Multiple alleles 1. Complicates dominance [Fig. 4.4] 2. Temperature sensitive alleles [Figs. 4.5, 4.6] E. Gene dosage effect [Exp. 4A] F. Codominance 1. ABO blood group: multiple alleles, dominant, recessive, codominant [Table 4.3]
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Unformatted text preview: G. Overdominance: heterozygote advantage [Figs. 4.9, 4.10] 1. Sickle cell and malaria resistance 2. Compared to hybrid vigor (heterosis) H. Penetrance and expressivity [Fig. 4.11, 4.12] 1. Environmental influences(?) [Fig. 4.13] 2. Modifier genes I. Hormonal influence on gene expression 1. Sex-influenced inheritance (observed in heterozygote) [Figs. 4.14, 4.15] 2. Sex-limited inheritance [Fig. 4.16] III. Gene interactions result in ‘modified’ Mendelian ratios (one gene product influences other gene expression/gene products) A. Bateson & Punnett experiment w/ comb shape in chickens [Fig. 4.17] B. Epistasis [Fig. 4.18] C. Calvin Bridges & Drosophila eye color [Exp. 4B, Fig. 4.19] IV. Study Suggestions A. Solved problems: S1 – S4 B. Conceptual problems: C1 – C6, C11 – C13, C15, C17 – C19, C22, C23, C27, C28 C. Experimental problems: E2, E9...
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BrookerChp4_ExtendedMendel - G Overdominance heterozygote...

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