Midterm IIs08key


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1 LS4 MIDTERM II INSTR: L. JOHNSON Monday, May 19, 2008 NAME:_________________________________ (last) (first) ID #___________________________________ INSTRUCTIONS 1. This exam is 6 pages long. Problem Score Before starting make sure you have all the pages. 1 18 2. No credit will be given for an 2 21 illegible answer. Please write in pen. 3 11 3. You may use a calculator. 4 13 5 24 6 13 Total 100
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2 Name _________________________________________ID#______________________ (last) (first) (18 pts) 1. All of the questions below are unrelated and worth 2 pts. No partial credit will be given. a) Two E. coli strains were mated: strain A ( arg - bio - cys + ade - ) and strain B ( arg + bio + cys - ade + ). The exconjugants are plated on MM+arginine+adenine. Most of the exconjugants are found to be arg - ade - . Which strain is the Hfr strain, A or B? Strain B b) Two reciprocal crosses are done. Cross I: Hfr a + b + c - x F - a - b - c + Cross II: Hfr a + b - c + x F - a - b + c - Cross II gives many more a + b + c + exconjugants than Cross I. What is the gene order? a-----c-----b c) What does it mean when two markers cannot be co-transduced? They are >1.5 minutes apart (or >2’ apart) d) In the cross Hfr lys - trp + x F - lys + trp - , prototrophs are selected for on minimal media. If these colonies are examined under the microscope, would they have pili? No e) In diploids, there is a limit of 50 mu which can be measured through genetic crosses. Is there a limit of 50 minutes in bacteria? No f) In generalized transduction, part of the phage genome is replaced with bacterial genes and transferred to the recipient cell via the phage infection (True or False). False g) To map phage genes, a bacteria is infected with two genetically distinct phage and parental and recombinant progeny phage are scored. Is this done at high MOI or low MOI? high
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This note was uploaded on 09/09/2008 for the course LIFESCI 4 taught by Professor Ribaya during the Summer '08 term at UCLA.

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