You are mapping the location of two genes in Drosophila,listless l and blind b.(l⁺ l⁺ b⁺ b⁺) and (l⁺ l b⁺ b) flies are normal,but (l l b b) flies don't move around very much and cannot detect the location of a light source.You perform a cross between a true-breeding normally active,sighted fly and a true-breeding listless,blind fly.You testcross an F1 individual with an individual homozygous recessive for both traits and get the following results:
Listless,sighted: 100
Listless,blind: 400
Normal activity,sighted: 400
Normal activity,blind: 100
The recombination frequency observed in experimental crosses can be used to indicate distances between genes on a chromosome.More specifically,the map distance in map units between two genes is equal to the frequency of recombinant offspring.What is the distance between these two genes?

Question

Quizplus · Accepted Answer

From the given data in the question, we observe that:
- Listless and blind traits are inherited together in double recessive individuals (llbb)
- The F1 generation resulting from a cross between a true-breeding normally active, sighted fly and a true-breeding listless, blind fly is heterozygous for both traits.
- The testcross result shows a 20% recombination frequency between the two genes.
Therefore, the two genes are 20 map units apart on the same chromosome.

You Are Mapping the Location of Two Genes in Drosophila,listless