Donkeys have a somatic chromosome number of 62. Hybrids produced by crossing donkeys and zebras are called zonkeys, are sterile, and have many characteristics intermediate between the two parental species. If a zonkey has 52 chromosomes, what is the somatic chromosome number of zebras?
A) 62
B) 42
C) 52
D) 31
E) 21

Question

Quizplus · Accepted Answer

The somatic chromosome number of zebras can be deduced by understanding that the chromosome number in hybrids (zonkeys) is the average of the chromosome numbers of the two parent species. Since donkeys have 62 chromosomes and zonkeys have 52, the chromosome number of zebras must be 42 (52 = (62 + X)/2, solving for X gives 42).

Donkeys Have a Somatic Chromosome Number of 62