100 BICD Spring 2008
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S. Brody, ext. 42619 4125 Muir Biology
HOMEWORK SET #7 (Covering lectures #22,23) Due Friday, May 30, 2008 ***PLEASE PUT YOUR NAME AND SECTION NUMBER IN INK OR TYPED ON TOP OF YOUR HOMEWORK SET*** 30 pts total (15 pts) 1. In a time of entry experiment, an Hfr lac+ pro+ pur+ strs strain was mixed with an F lac pro pur strr strain and the mixture plated at intervals on a media which allows all streptomycin resistant colonies to grow (i.e., pur+ or ; pro+ or ; lac+ or ). The following results were obtained (after replica plating).
100 80 Frequency of traits from Hfr parent 60 40 20 pro = proline requirer pur = purine requirer lac = lactose non-fermenter (can grow on glucose) pro+ lac+ pur +
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At 25 minutes, a sample is plated on minimal medium to which proline, lactose and streptomycin has been added and containing an indicator dye on which colonies that can ferment lactose turn red and those that cannot remain white (A). When these colonies had formed, they were replica plated onto a second plate of minimal medium to which only lactose and the indicator had been added (B). The results are indicated below: solid circles are lactose-fermenting, and open circles nonlactose fermenting colonies.
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BICD 100 Spring 2008
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S. Brody, ext. 42619 4125 Muir Biology
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Show the number and types (genotypes) of the colonies on Plate A. Put your answers on the sheet you hand in. Colony Type Genotype Number Seen
__________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ __________________________________________________________________________ b) (15 pts) 2. The Mariner space probe sent word back to Earth that 4 new Hfr strains of a Martian bacteria were isolated. It was also found that transduction could occur in this bacteria employing a phage from Earth. Since the geneticists were interested in whether the fine structure of a gene was the same for Martian bacteria as for our homegrown ones, they isolated some more strains. They obtained 2 mutants altered in the same gene, J auxotrophs, designated J1 and J2, then they constructed a strain of this genotype ENJ1 which was then transduced by a phage grown on a strain of EN+J2. They got EN+J+ colonies out of this transduction in reasonable numbers (500). They also did the opposite transduction, i.e., phage grown on ENJ1 was used to transduce the strain EN+J2. This also yielded 500 EN+J+ colonies. At this point, some of the scientists quit the project and took up astrology instead. However, some of them were able to deduce the order of the J mutations with respect to the EN gene. See if you can do it as well. Illustrated how you got this order with the appropriate diagrams. Label clearly donor and recipient sections with the markers on them. Construct a recombination map of the three markers from these data. Show the percentage recombination between pur and lac and between lac and pro.
Transduction #1 ENJ1 EN+ J2 Result 500 Colonies 2 #2 EN+ J2 ENJ1 Result 500 Colonies
Recipient Exogenate
BICD 100 Spring 2008
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S. Brody, ext. 42619 4125 Muir Biology
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