Let\'s say you are studying the genes dpy-3. unc-2. and If you expect 0.15 cross

Question

Let's say you are studying the genes dpy-3. unc-2. and If you expect 0.15 crossover events per meiosis between the genes dpy-3 and unc-2, how many centimorgans separate the genes. If you expect 0.05 crossover events per meiosis between the genes unc-2 and rol-7, how many centimorgans separate these genes? 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?

Explanation / Answer

Centimorgan (c.M), also referred to map units (m.u) is used in genetics to infer linkage between two genes. It corresponds to the distance between the two loci on the chromosome. 1 c.M equals to 0.01 crossover events between the genes per meiosis event.

(a) Per meiotic event, there is 0.15 crossover event between genes dpy-3 and unc-2.

Therefore, distance between them is 15 (0.15/0.01) c.M

(b) Per meiotic event, there is 0.05 crossover event between genes unc-2 and rol-7.

Therefore, distance between them is 5 (0.05/0.01) c.M

(c) Given, the order of the gene is D-U-R

When D-u-r//d-U-R is crossed to d-u-r, the phenotype classes observed would be:

Parental type, single crossover type and double crossover type (rare)

(d) The parental type and single crossover type would be most frequent phenotype classes in the offsprings.

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