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Unformatted text preview: 1 LS4 Midterm II INSTR: L. Johnson Monday, Feb. 26, 2007 NAME:_________________________________ (last) (first) I.D. #__________________________________ INSTRUCTIONS 1. This exam is 8 pages long. Problem Value Score Before starting make sure you have all the pages. 1 10 2. Be sure to write clearly. Only 2 14 legible answers will be graded. 3 1 2 4 8 5 6 6 30 7 20 Total 100 KEY 2 NAME:_________________________________ ID# _______________________ (last) (first) (10 pts) 1. You have an E. coli strain (A) which is either HfrH (str-s) or carries an F'801(ser + thr + but does not contain genes from leu through lys), which was derived from HfrH (see map below where arrowhead indicates origin of transfer). Describe a genetic cross that would let you distinguish between these two possibilities. Assume that both strains are prototrophic. You can use any other strain(s) of E. coli you wish. In your experiment, be sure to say what marker you use to select for the exconjugants and against the male parent. Strain A x F- str-r thr- ser- select on MM plus streptomycin and serine. Replica plate onto MM. If all the colonies that grew on the master plate can also grow on MM, then the strain is F801. If most of the colonies cannot grow on MM, then the strain is HfrH. (14 pts) 2. A cross between an Hfr str-s arg + lac + leu- and F- str-r arg- lac- leu + is plated on minimal media plus streptomycin and leucine (arginine is the last marker to be transferred). 700 colonies grow and are then replica plated on minimal media (500 grow), minimal media plus lactose (0 grow) and minimal media plus lactose and leucine (150 grow). a) Write the four genotypes you expect to find in the exconjugants and the number of each observed. (+8 pts) arg + leu + lac + 500 arg + leu + lac- 150 arg + leu- lac + 50 arg + leu- lac- b) What is the order of the genes? arg-leu-lac (+2 pts) c) What is the recombination frequency between arg and lac? (+2 pts) 500+50/700 = 79% d)...
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This note was uploaded on 07/13/2008 for the course LS 4 taught by Professor Ribaya during the Spring '08 term at UCLA.
- Spring '08