Pract Prob Set 2B lect 14-19 Answers

Pract Prob Set 2B lect 14-19 Answers - ANSWERS Pract Prob...

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ANSWERS Pract Prob Set 2B Bio61 Geoff Lectures 14-19 1. Campbell–see answers in book 2. How is polygenic inheritance somewhat the opposite of pleiotropy? Pleiotropy is a situation where an allele of one gene affects seemingly unassociated characters. On the other hand, polygenic inheritance is a situation where the alleles of many genes affect juts one character (i.e. height, skin color) 3. The gene for eye color, represented by the alleles G (green) and g (blue), is linked to some degree to the gene for wing shape, represented by the alleles V for v-shape and v for round shape. Assume complete dominance. A green, v-shaped individual is crossed with a blue round shaped individual. The progeny are 40% green and round, 40% blue and v-shaped, 10 % green and v-shaped, and 10% blue and round. Explain these results. The blue, round parent must be ggvv. All its gametes must carry gv. Since there is some degree of linkage but not extreme linkage, some recombination has occurred. If all of one parent’s gametes are giving g and v, then to have the resulting phenotypes, 40 % of other parent’s gametes must be Gv and gV and 10 % must be GV and gv. The GV and gv gametes must come from recombinants. Thus, the original parents must have G and v linked on one homolog and g and V linked on the other homolog. 4. The disease telephontia is caused by a sex-linked allele of a gene. A man with telephontia and a healthy woman have three daughters, all who have the disease. Explain the result. The disease allele is most probably dominant. It is on the X chromosome. The daughters will get an X from mom and an X from dad. Since mom is OK, either the disease allele is recessive or she has no dominant disease alleles. Since she contributed an X to each daughter and all daughters have the disease, chances are that telephontia is caused by a dominant allele. If it is recessive, then it would mean that all 3 daughters got a copy of the X from mom that carries the recessive allele. The chance of this is slim (1/2 x ½ x1/2). Thus, the best explanation is that it is a dominant disease allele that causes telephontia. Since dad carries only 1 X, you really cant tell from him whether tis is recessive or dominant 5. Female mammals are considered____mosaics_______ because in some other cells the paternal X is inactivated while in other cells the maternal X is inactivated. 6. Autosomal aneuploidy usually results in serious consequences while sex chromosome
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This note was uploaded on 05/01/2008 for the course BIO 61 taught by Professor Geoff during the Spring '08 term at Pacific.

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Pract Prob Set 2B lect 14-19 Answers - ANSWERS Pract Prob...

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