EXAM 3 answers

EXAM 3 answers - Biology 313, Fall 2010 Exam 3, Nov 15,...

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Biology 313, Fall 2010 Exam 3, Nov 15, 2010 Name _____________________________Score: _________________ This exam has 100 total points Multiple Choice (2 points each): Circle the correct answer. 1. A mouse/human heterokaryon is placed in tissue culture and allowed to divide a large number of time/ What will be observed? a. An allotetrapolid will form. b. There will be a high degree of aneuploidy for the human chromosomes. c. An embryo will develop that can be implanted in a recipient mother until birth. d. The autopolyploid will be stable but will not be able to undergo meiosis. e. Mouse chromosomes will be lost. 2. One cM in Arabidopsis corresponds on average to 100 kbp . You perform two point crosses and find that two genes, ( A ) and ( B ), are linked and separated by 20 cM. You also perform deletion mapping and find that (A) and (B) are both encompassed by a 300 kbp deletion. What is the best explanation of your results? a. The data are consistent and show that (A) and (B) are 20 cM apart. b. Recombination frequencies are usually less than physical distances because of interference. c. Large chromosomal deletions are often caused by X-rays that can confuse the results of two point crosses because of deletion loops during Prophase I. . d.The data suggest that the region between (A) and (B) is a hotspot of recombination. e. It is not surprising that cM and kbp do not correspond, since one is the reciprocal of the other. 3. You perform a deletion mapping experiment to determine the location of gene “A” on chromosome 3 of the model organism C. elegans , a nematode (worm) You cross a male that is homozygous recessive with a series of females that are heterozygous for different 200 kbp deletions of chromosome 3 (lines 1, 2, 3 and 4). The males have an “a” phenotype while the females have an “A” phenotype. In the F1 you score the progeny for the “A” or “a” phenotype and observe that ALL of the F1 progeny, regardless of the cross, have an“A” phenotype. How do you explain these results? a. Gene “A” resides outside the regions of chromosme 3 encompassed by deletions 1-4. b. Lines 1-4 are haploinsufficient for gene “A”. c. “a” is an example of a pseudodominant gene. d. Gene “A” could be present in many tandemly repeated copies, typical of moderately repetitive DNA. e. Two of the above offer sound explanations of the data. 1
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4. A panel of cell lines was created from mouse-human somatic-cell fusions. Each line was examined for the presence of human chromosomes and for the production of an enzyme. The following results were obtained: On the basis of these results, which chromosome has the gene for the enzyme? a. 1 b. 5 c. 8 d. 17 e. 22 Questions 5-9 . Consider the following chromosome, where represents the centromere. A B
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EXAM 3 answers - Biology 313, Fall 2010 Exam 3, Nov 15,...

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