Richmond Hill, Canada

#1 Mar 28, 2012
An extraterrestrial scientist is trying to obtain a genetic map of a newly discovered bacterium using standard techniques such as interrupted conjugation and Hfr mapping. She is particularly interested in three loci (ata, tic, and lan) encoding proteins that are required for the synthesis of atanine, ticovine, and lancytrine (three essential extraterrestrial amino acids), respectively. With the help of interrupted-conjugation experiments, the scientist determines that ata is the last marker to enter the recepient bacterium. She now sets up a cross between a wild type Hfr strain that is tertacycline sensitive and an ata-tic-lan- F- strain that is tetracycline resistant. 5000 exconjugants are recovered on minimal medium plus tetracycline, ticovine, and lancytrine, and subsequently replica-plated onto a variety of media. The results are as follows:

- minimal medium and tetracycline: 4704 colonies grow;
- minimal medium plus lancytrine and tetracycline: 4708 colonies grow;
- minimal medium plus tetracycline and ticovine: 4900 colonies grow.

a) Draw a genetic map of these three loci (including all the map distances).
b) What is the purpose of the tetracycline?
c) What is the purpose of excluding atanine from the minimal medium?

Would someone please help me understand what this is asking/solve the problem for part a.

Thank you :)

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