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:

42

Explanation:

The somatic chromosome of zebras will be 42.

During gamete formation prior to fertilization, reproductive cells divides by meiosis to give rise to haploid cells with half the number of chromosomes of the somatic cells.

During fertilization, two haploid gametes fuse together to give rise to a diploid zygote.

A donkey with 62 somatic chromosome will produce gametes with 31 chromosomes. Zonkey is a diploid organism and has chromosome number of 52, hence, the haploid gamete of zebra would have:

52 - 31 = 21 chromosomes.

Hence, the diploid (somatic) chromosome number of zebras will be:

21 x 2 = 42 chromosomes.