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Unformatted text preview: BICD 100 Spring 2008 30 pts total 1. a) Page 1 of 4 HOMEWORK SET #6 -- KEY S. Brody, ext. 42619 4125 Muir Biology (14 pts total) (2 pts) Let b = bristles missing, n = nicked wings, the transmission is typical sex-linkage, thus P1 generation: (female) F1 bn bn bn Y and X++ Y ++ bn (male) b) (2 pts) The 2:1 sex ratio in the F2 suggests that the F1 female received from her father an X chromosome bearing a recessive lethal. (5 pts) The order of b, n and l (lethal) may be one of three possibilities:
1 2 3 c) + b n ________ l + + b + n _______ + l + b n + _______ + + l Double recombinants would be:
1 2 3 Genotype Phenotype Observed ++n +nl nicked lethal 9 lb+ lethal 0 bln lethal 0 +++ normal 7 b++ bristles 1 0 Since the rare class (i.e., the product of double exchange) is missing bristles, normal wing, then order 3 is indicated. BICD 100 Spring 2008 d) (5 pts) Page 2 of 4 S. Brody, ext. 42619 4125 Muir Biology b-n = 1 + 9 = 20 m.u. 50 n-1 = 1 + 7 = 16 m.u. 50 double single b 20 n 16 l ___________________ 0.0 20.0 36.0 2. (4 pts total) a) Designate the chromosomes as AA'aa'. The types of gametes then would be: Aa; A'a'; AA'; aa'; Aa'; A'a. This assumes no crossing over between A (or a) and the centromere and equal disjunction of all 4 chromosomes. The sum of the gametes would then be 5A_:1aa, which would give phenotype ratio of 5A:1a since it is a test cross. (4 pts) 3. a) Let XT be an X chromosome with the mutant allele. Xt has the normal allele. (12 pts total) (1 pt) I-1 is XTY II-1 is XTXt (1.5 pts) III-1 is XTY -- but see (c) below III-2 is XTXt III-5 is XtXt (3.5 pts) Some or all of the germ cells of III-1 must carry a translocation between the X and an autosome such that the X no longer carries T (such an X is now X0) but the autosome does (AT versus A normal). (2 pts) IV-4 is XtX0, AA IV-5 is XtY, ATA e) (4 pts) V-9 is XtXt, AA V-10 is XtY, ATA V-11 is XtY, AA V-12 is XtXt, ATA b) c) d) ...
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This note was uploaded on 06/07/2008 for the course BICD 100 taught by Professor Nehring during the Spring '08 term at UCSD.
- Spring '08