BICD 100midterm2 practice

BICD 100midterm2 practice - BICD 100 - Genetics, Summer...

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BICD 100 - Genetics, Summer Session I, 2005 Key to Second Midterm Examination, Version A For each question, write the letter or number corresponding to the correct answer on your answer sheet. You are welcome to use scratch paper, but you may not turn it in. Turn in only the answer sheet. Six recessive mutants of Drosophila are represented by the symbols a, b, c, d, e and f. In the following several questions, you are to interpret the data derived from the crosses described below in terms of the linkage relationships of the six genes, integrating all of the data presented. 1 (2 pts). In the first cross, males with only recessive alleles at all six loci were mated to homozygous wildtype females. All F1 individuals were completely wildtype. F1 males were then mated to homozygous recessive females with the following results. The top row indicates which recessive traits were seen. For example, “e” means the flies showed only the recessive trait due to allele e, while for all other loci only the dominant trait was seen. wildtype e abd abde cf cef abcdf abcdef Females 48 40 43 44 0 0 0 0 Males 0 0 0 0 40 42 39 41 These data indicate that a) c and f are Y linked, while a, b, d and e are X linked b) c and f are X linked, while a, b, d and e are Y linked c) c and f are Y linked, while a, b, d and e are autosomal d) c and f are X linked, while a, b, d and e are autosoma l e) all 6 are autosomal f) all 6 are X linked g) impossible to tell which loci are on the X, Y or autosomes h) some other answer The daughters have, but the sons have not, inherited the wildtype alleles of c and f from their fathers. 2 (2 pts). The data above indicate that a) a and b are syntenic b) a and b are linked c) a and e are syntenic d) a and e are linked e) all 6 are independently assorting f) a, b, d and e are all independently assorting g) more than one of the preceding h) none of the preceding i) not enough information to answer Syntenic loci are inherited as a unit from male Drosophila, whether they are close enough to be linked or not. This is so because of the lack of crossing over in Drosophila males. 3. (2 pts). F1 females from the original cross (beginning of question 1) were crossed to completely recessive males. Thirty three different types of progeny arose, and there was no difference between male and female progeny in which phenotypes were seen. More phenotypic types result from this cross than from the cross in question 1 because a) the F1 males in #1 were homozygous at more loci than the F1 females b) syntenic loci segregate together when passed by Drosophila males, but not female s c) syntenic loci segregate together when passed by Drosophila females, but not males d) more than one of the preceding e) none of the preceding f) not enough information to answer 4 (2 pts). A total of 1473 progeny were obtained from the cross in question 3. The most frequently observed types, representing 1072 progeny (about 134 each), were the following eight kinds (again,
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This note was uploaded on 04/08/2008 for the course BIBC 100 taught by Professor Nehring during the Spring '07 term at UCSD.

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BICD 100midterm2 practice - BICD 100 - Genetics, Summer...

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