Danielle 4-5

Danielle 4-5 - Homework (due Feb 13!) Required Problems...

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Homework (due Feb 13!) Required Problems 4.3, 4.5, 4.7, 4.8, 4.10, 4.12, 4.13, 4.18, 4.20, 4.21, 4.26, 4.27, 4.28. 25.1, 5.1, 5.4, 5.6, 5.7, 5.10, 5.12, 5.13, 5.17, 5.22 Problems on posted assignment. Recommended: 3.17, 3.18, 3.23, 3.25, 4.1, 4.2, 4.9, 4.11, 4.14, 4.17, 4.25, 5.8, 5.9, 5.11, 5.15.
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Ch. 4. Extensions of Mendelism Fig. 4.1 Incomplete dominance: a type of inheritance in which both alleles for a specific trait are expressed. This results in a combined phenotype. Incomplete dominance: Heterozygote has phenotype different from either homozygote. Heterozygote has its own phenotype- usually a blending of the 2 homozygotes Genetic basis of flower color is snapdragons. The allele W is incompletely dominant over w. Differenences among the phenotypes could be due to the differences in the amount of the product specified by the W allele
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More on incomplete dominance As we talked about previously, dominance describes a specific relationship between the effects of different versions of a gene (alleles) on a trait (phenotype). Animals, as we discussed, are diploid, with two copies of each gene, one inherited from each parent. If the two copies are not identical (not the same allele), their combined effect may be different than the effect of having two identical copies of one or the other allele. But if the combined effect is the same as the effect of having two copies of one of the alleles, we say that the allele's effect is dominant over the other.
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Fig. 4.2 Codominance: A condition in which both alleles of a gene pair in a heterozygote are fully expressed, with neither one being dominant or recessive to the other. Both alleles independently detectable in heterozygote. A good example of codominance is blood group alleles. •M serum binds to M- protein and N serum binds to N-protein •Heterozygotes clump in this case since they have both proteins on their surfaces •Detection of the M and N antigens on blood cells with specific anti-sera. With the anti-M and anti-N sera, three blood types can be indentified
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Multiple alleles of a single gene For simplicity’s sake, genetics is usually taught using examples with only two possible alleles (A and a). However, a single gene can actually have many possible alleles (A, a, A1, A2, A', etc.). For example, hair color in mice is determined by a single gene with a series of alleles, each resulting in different coloration. There are alleles for black, brown, agouti, gray, albino, and others. The twist here is that the same allele can be dominant or recessive depending on context. Allelic series are often written as agouti > black > albino. This means that agouti is dominant to black, and black is dominant to albino.
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This note was uploaded on 03/30/2008 for the course BIOL 2156 taught by Professor Larkin during the Spring '08 term at LSU.

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Danielle 4-5 - Homework (due Feb 13!) Required Problems...

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