Question

Diploid somatic cells of elephants have 56 chromosomes. If nondisjunction of one of an elephant's chromosomes occurs in meiosis I, the resulting sperm are expected to have the chromosome complement:

a. 29, 29, 27, 27.
b. 56, 56, 57, 55.
c. 28, 28, 29, 27.
d. 29, 29, 28, 28.

Answer 1

a. 29, 29, 27, 27.

Step-by-step explanation:

Separation of homologous chromosomes to the opposite poles during anaphase-I would have produced the haploid chromosome number of the daughter cells. This means that the parent cell with 56 chromosomes would produce four daughter cells each of which would have 56/2= 28 chromosomes. If one of the chromosome pairs did not segregate during anaphase-I, one daughter cells formed by the end of meiosis-I would have "n+1" chromosomes while the other would have "n-1" chromosomes. This chromosome number is maintained by meiosis-II.

Therefore, nondisjunction at anaphase-I in the parent cell with 56 chromosomes would produce a total of four daughter cells. The two daughter cells would have "n+1= 29" chromosomes and rest two would have "n-1=27" chromosomes.