Could someone help me with this problem, please I\'ve forgot how to do this. tha
ID: 71292 • Letter: C
Question
Could someone help me with this problem, please I've forgot how to do this. thank you
A drosophila geneticist crossed females homozygous for three X-linked mutations ( y, yellow body; B bar eye shape; v, vermilion eye color) to wild-type males. The F1 females which had gray bodies and bar eyes with dark red pigment, were then crossed tot yB+v males, yielding the following results:
Phenotype Number
yellow, bar, vermilion wild type 546
yellow bar, vermilion 244
yellow, vermilion bar 160
yellow, bar vermilion 50
Determine the order of these three loci on the X chromosome and estimate the distance between them.
Explanation / Answer
All mutations are X-linked. We know that Drosophila males are hemizygous.
Parent female is homozygous and has the genotype yyBBvv
It is crossed to male, having genotype y+B+v+
F1 result is yy+BB+vv+ (gray, bar eyes, dark red pigment) for females and yBv (yellow, bar eye, vermilion) for males
F2 cross is yy+BB+vv+ (female) crossed with yB+v (male)
All the phenotypes given in your data are yellow, bar and vermilion. This means that no recombination has occurred in the female (which is impossible under normal conditions). Without recombination, recombination frequency and distance between the three loci cannot be found out. Kindly check your data.