Question

In D. virilise, the mutations dusky body (dy), cut wings (ct) and white eyes (w) are all recessive alleles located on at different places on the x chromosome. Females heterozygous for all three mutations were crossed to dy ct w males, and the following phenotypes were obtained

Class Phenotype Number
1 Wild type 18
2 Dusky 153
3 cut 6
4 White 76
5 cut, white 150
6 dusky,cut 72
7 dusky,cut,white 22
8 dusky,white 3

(i) What are the genotypes of the two maternal X chromosomes?
(ii) What is the map order of the genes on the X chromosome?
(iii) What are the two-factor recombination frequencies between each pair of genes?
(iv) Are there as many observed double-crossover gametes as you would expect if there was no interference?
(v) What is the coefficient of coincidence and interference in this region?

Answer 1

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