Question

for a child to be born XXY, there must have been a mistake during gamete formation in one of the parents.  Suppose the egg was normal, and the mistake was during the formation of the SPERM. Consider the germ cell that went through meiosis to make this problematic sperm. Focus only on the sex chromosomes (do not draw the other 22 pairs of chromosomes). The mistake is either in Anaphase I or Anaphase II. Determine which one it is.  Draw Anaphase I, the cells at the end of meiosis I, Anaphase II, and the 4 haploid cells, and mark the problematic sperm.

PLEASE draw neat and clear & thank you:)

Answer 1

Female has two X-chromosomes. So ovum will only have X chromosome. So, the male sperm has given XY chromosome to the zygote.

As shown in the figure, if non-disjunction could have occurred in anaphase-I then the sperm have XY chromosomes. If non-disjunction could have occurred in anaphase-II then male sperm could have either XX or YY chromosomes.

Since the genotype of the zygote is XXY. So, non-disjunction has occurred in anaphase-I