Question

if non disfunction of chromosome 21 is known to occur in division of secondary oocyte in a particular women then what is the chance that a mature egg arising from this cell division will receive 21 chromosomes​

Answer 1

Explanation:

Down syndrome (trisomy 21)

The majority of cases result from nondisjunction during maternal meiosis I. Trisomy occurs in at least 0.3% of newborns and in nearly 25% of spontaneous abortions. It is the leading cause of pregnancy wastage and is the most common known cause of mental retardation.