If a pair of homologous chromosomes fails to separate during anaphase of meiosis I, what will be the chromosome number of the four resulting gametes with respect to the normal haploid number (n) ?

If a pair of homologous chromosomes fails to separate during anaphase of meiosis I, what will be the chromosome number of the four resulting gametes with respect to the normal haploid number (n) ?

a) n + 1; n + 1; n - 1; n - 1

b) n + 1; n + 1; n; n

c) n + 1; n - 1; n; n

d) n + 1; n - 1; n - 1; n - 1

Answer:

a) n + 1; n + 1; n - 1; n - 1

Explanation:

Separation of homologous chromosomes occurs during anaphase-I of meiosis. This event reduces the chromosome number from 2n to "n" in the daughter cells. If a pair of homologous chromosomes do not separate during anaphase-I, both the homologous chromosomes of that pair would be present in one daughter cell of the meiosis-I (n+1) while the other daughter cell would lack that chromosome (n-1).

Meiosis-II would maintain this chromosome number. Therefore, two gametes will have one extra chromosome (n+1) while the two gametes would lack one chromosome (n-1).