The two loci Y (y)and R (r)are normally 20 map units apart.A particular dihybrid individual is heterozygous for an inversion that spans 98% of the region between Y and R,but does not include Y or R.If this dihybrid is testcrossed to an individual with normal chromosomes,the recombinant frequency in progeny will be:
A)more than 20%.
B)20%.
C)less than 20%,but more than 10%.
D)10%.
E)less than 10%.

Question

Quizplus · Accepted Answer

Inversions suppress recombination within the inverted region. Since the inversion spans 98% of the region between Y and R but does not include these loci, recombination is suppressed in most of the region between them. However, because Y and R are not within the inversion, the only recombination that can occur is in the small regions outside the inversion, leading to a recombinant frequency significantly lower than the original 20%, thus less than 10%.

The Two Loci Y (Y)and R (R)are Normally 20 Map