In Drosophila, a cross was made between females—all expressing the three X-linked recessive traits scute bristles (sc), sable body (s), and vermilion eyes (v)—and wild-type males. In the F1, all females were wild type, while all males expressed all three mutant traits. The cross was carried to the F2 generation, and 1000 offspring were counted, with the results shown in the following table. Phenotype Offspring sc s v 314 + + + 280 + s v 150 sc + + 156 sc + v 46 + s + 30 sc s + 10 + + v 14 No determination of sex was made in the data. (a) Using proper nomenclature, determine the genotypes of the P1 and F1 parents. (b) Determine the sequence of the three genes and the map distances between them. (c) Are there more or fewer double crossovers than expected? (d) Calculate the coefficient of coincidence. Does it represent positive or negative interference?
In Drosophila, a cross was made between females—all expressing
the three X-linked recessive traits scute bristles (sc), sable body (s),
and vermilion eyes (v)—and wild-type males. In the F1, all females
were wild type, while all males expressed all three mutant traits.
The cross was carried to the F2 generation, and 1000 offspring
were counted, with the results shown in the following table.
sc s v 314
+ + + 280
+ s v 150
sc + + 156
sc + v 46
+ s + 30
sc s + 10
+ + v 14
No determination of sex was made in the data.
(a) Using proper nomenclature, determine the genotypes of the P1
and F1 parents.
(b) Determine the sequence of the three genes and the map distances
between them.
(c) Are there more or fewer double crossovers than expected?
(d) Calculate the coefficient of coincidence. Does it represent
positive or negative interference?
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