In guppies, fan tail is dominant to flesh tail, and rainbow color is dominant to pink. F₁ female guppies are crossed with flesh-tailed, pink-colored males, and the following progeny are observed: 401 fan-tailed, pink-colored; 399 flesh-tailed, rainbow-colored; 98 flesh-tailed, pink-colored; and 102 fan-tailed, rainbow-colored guppies. Assuming that the F₁ female guppies have both dominant alleles on one chromosome, the map distance between these two genes is A) 80 cM. B) 25 cM. C) 0.8 cM. D) 20 cM. E) None of the above

Question

Quizplus · Accepted Answer

The map distance between two genes is calculated as the percentage of recombinant offspring. In this case, the recombinant offspring are the flesh-tailed, pink-colored and fan-tailed, rainbow-colored guppies. The total number of offspring is 401 + 399 + 98 + 102 = 1000. The number of recombinant offspring is 98 + 102 = 200. Therefore, the map distance between the two genes is 200/1000 * 100 = 20 cM.

In Guppies, Fan Tail Is Dominant to Flesh Tail, and Rainbow