Question

The mating of an Aa male and an aa female produced an offspring with the genotype aaa. Therefore, the resulting offspring has 3 copies of gene 1 (trisomy for chromosome 1). At what stage during meiosis did the non-disjunction event occur and in which parent? There may be multiple answers.

a. Paternal non-disjunction in meiosis I

b. Materinal non-disjunction in meiosis I

c. Paternal non-disjunction in meiosis II

d. Maternal non-disjunction in meiosis II
b, c, d

The female sign points (down/up) and the male sign points (down/up).
Down; up

Answer 1

Materinal non-disjunction in meiosis I

Paternal non-disjunction in meiosis II

Maternal non-disjunction in meiosis II