Question

Inheritance patterns cannot always be explained by Mendel's models of inheritance. If a pair of homologous chromosomes fails to separate during meiosis I, select the choice that shows the chromosome number of the four resulting gametes with respect to the normal haploid number (n)?

Answer 1

The question is incomplete as it does not have the options which are:

A) n+1; n+1; n-1; n-1

B) n+1; n-1; n; n

C) n+1; n-1; n-1; n-1

D) n+1; n+1; n; n

Answer:

Option-1

Explanation:

The laws of inheritance were concluded from the result of Mendel's experiment which is based on the fact that gametes are formed. Later research suggested that gametes are formed by the process of meiosis which takes place in two phases and recombination is a characteristic of Meiosis.

If during anaphase I of meiosis I, the alleles fails to separate that is nondisjunction takes place at anaphase I, Then the resulting daughter cells will have unequal distribution of chromosomes.

One daughter cell will receive 1 extra copy of the chromosome while another daughter cell will receive 1 less chromosome therefore ploidy level will be n+1 and n-1.

During meiosis II, 2 more daughter cells will be formed with the same ploidy level therefore in last the meiosis will result in 2 (n+1) and 2 (n-1) cell.

Thus, Option-1 is the correct answer.