Somatic cells of individuals with Down's syndrome usually have an extra chromosome 21; they contain 47 chromosomes. At which stage(s) of meiosis

Somatic cells of individuals with Down's syndrome usually have an extra chromosome 21; they contain 47 chromosomes. At which stage(s) of meiosis could a mistake alter the chromosome number?

AnswerActually, separation of homologous chromosomes occurs during metaphase I while, separationof chromatids occurs in metaphase II. So, these are the phases in which non-disjunction may be...