Question

A cell undergoing meiosis produces four daughter cells, two of which are aneuploids, while two are haploid. This can occur due to

• A. non-disjunction during first meiotic division only
• B. non-disjunction during second meiotic division only
• C. non-disjunction during either first or second meiotic divisions
• D. non-disjunction during both first and second meiotic divisions.

Answer 1

Answer: (A)

The process of separation of homologous chromosomes during anaphase-I is referred to as disjunction. This process is responsible for reducing the chromosome number to half. Failure of occurence of this process i.e. non-disjunction results in failure of homologous chromosomes to separate, so that one gamete comes to have an extra chromosome (N + 1) while the other becomes deficient in one chromosome (N -“ 1). This results in the production of aneuploids.