Introduction to Genetic Analysis 545

Introduction to Genetic Analysis 545 - by X rays, and two

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544 Chapter 16 Dissection of Gene Function Explain the possible molecular-genetic basis of these three mutant categories, inventing examples where possible. 41. In Drosophila, the genes for ebony body ( e ) and stubby bristles ( s ) are linked on the same arm of chromosome 2. Flies of genotype 1 s/e 1 develop predominantly as wild type but occasionally show two different kinds of unexpected abnormalities on their bodies. The ±rst abnormality is the presence of pairs of adjacent patches, one with stubby bristles and the other with ebony color. The second abnor- mality is the presence of solitary patches of ebony color. a. Draw diagrams to show the likely origin of these two types of unexpected abnormalities. b. Explain why there are no single patches that are stubby. ( Hint: What would be the outcome of a crossover between homologs that accidentally pair at mitosis ?) 42. A strain of Aspergillus was subjected to mutagenesis
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Unformatted text preview: by X rays, and two tryptophan-requiring mutants (A and B) were isolated. These tryptophan-requiring strains were plated in large numbers to obtain rever-tants to wild type. You failed to recover any rever-tants from mutant A and recovered one revertant from mutant B. This revertant was crossed with a normal wild-type strain. a. What proportion of the progeny from this cross would be wild type if the reversion precisely re-versed the original change that produced the trp 2 mutant allele? b. What proportion of the progeny from this cross would be wild type if the revertant phenotype was produced by a mutation in a second gene located on a different chromosome (the new mutation sup-presses trp 2 )? c. Propose an explanation of why no revertants from mutant A were recovered. (Dana Burns-Pizer.) 44200_16–p521-544 3/17/04 9:12 AM Page 544...
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This note was uploaded on 01/10/2011 for the course BIOL BIOL taught by Professor Johnson during the Spring '08 term at Aberystwyth University.

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