Let\'s say you are studying the genes dpy-3, unc-2 and rol-7 in C. elegant. If y

Question

Let's say you are studying the genes dpy-3, unc-2 and rol-7 in C. elegant. If you expect 0.15 crossover events per meiosis between the genes dpy-3 and unc-2, how many centimorgans separate the genes? _ cM If you expect 0.05 crossover events per meiosis between the genes unc-2 and rol-7 how many centimorgans separate these genes? _cM If the order of the genes is D-U-R, mutants of each of these genes are recessive, and a wildtype heterozygote with the phase (D u r//d U R) is crossed with a triple mutant, what phenotypic classes would you expect to observe in the offspring? What would be the two most frequent phenotypic classes? You are interested in Drosophila genes involved in vision. If you subject flies to EMS and kill off offspring that can see attractive light sources in order to select for poor vision mutants, you are conducting a _ screen. Let's say you are mapping the location of one of your mutations that causes blindness using a testcross. You get counts of offspring phenotypes that suggest that your two markers are so close to the mutation that they seem like they are on top of it. In one sentence, explain what those counts of offspring phenotypes would need to have been in order to draw that conclusion.

Explanation / Answer

15.

(a) 0.15 recombination implies 15cM distance between genes.

(b) 0.05 recombination implies 5cM distance between unc-2 and rol-7.

(c) Mutants of the gene D-U-R are recessive. Triple mutants will be d-u-r.

If wild type heterozygote D-u-r is crossed with d-u-r, then possible offsprings are:

D-u-r, d-u-r

If wild type heterozygote d-U-R is crossed with d-u-r, then possible offsprings are:

d-U-r, d-u-R= recombinants

d-U-R, d-u-r= parentals

(d)Two most frequent phenotypes are parentals= d-u-r and D-u-r/d-U-R

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