In Drosophila,the allele red eyes (bw+)is dominant to the allele for brown eyes (bw).At another gene locus on the same chromosome,the allele for thin wing veins (hv+)is dominant to the allele for heavy wing veins (hv).Flies homozygous for bw and hv+ are crossed to flies homozygous for bw+ and hv to obtain doubly heterozygous F 1 progeny.
-What is the relationship between recombination frequency and the actual physical distance on a chromosome?
A)As physical distance increases,the recombination frequency increases in a linear fashion.
B)As physical distance increases,the recombination frequency decreases in a linear fashion.
C)As physical distance increases,the recombination frequency first increases in a linear fashion,but gradually levels off to a frequency of 0.5.
D)As physical distance increases,the recombination frequency first increases,but then decreases.

Question

Quizplus · Accepted Answer

Recombination frequency increases with physical distance between genes up to a point, but due to the maximum limit of 50% (which is equivalent to the recombination rate for genes on different chromosomes or far apart on the same chromosome), it levels off, reflecting the fact that distant genes assort independently.

In Drosophila,the Allele Red Eyes (Bw+)is Dominant to the Allele