Question

When maternal and paternal chromosomes fail to separate correctly during meiosis leading to defective chromosome number in gametes, it is called...... Select one: a. homologous recombination b. gene conversion c. independent assortment d. transposition e. nondisjunction

Answer 1

Answer is E - non disjunction

During Nondisjunction pair of homologous chromosomes fail to separate during anaphase stage so that both chromosomes of the pair pass to one daughter cell.

Disorders caused due to Nondisjunction are trisomy 21 (Down syndrome) and monosomy X (Turner syndrome).

Down's syndrome - A genetic disorder caused by the presence of third copy of chromosome 21. Symptoms include growth retardation and intellectual disability

Turner syndrome is caused when one of the X chromosomes is missing.  It result in the failure of the ovaries to develop, short height and severe heart diseases.

Nondisjunction also leads to early spontaneous abortions.