In the hexaploid wheat, the haploid $(n)$ and basic $(x)$ numbers of chromosomes are

Which of the following disorders exhibits sex chromosomal monosomy?

$A$ mother has Down syndrome,and the father is normal. What is the probability of their offspring having Down syndrome (in $\%$)?

Match Column $-I$ with Column $-II$ and select the correct option.

Column $-I$	Column $-II$
$(P)$ Turner syndrome	$(i)$ Sex chromosome $(2n-1)$
$(Q)$ Down syndrome	$(ii)$ Sex chromosome $(2n+1)$
$(R)$ Klinefelter syndrome	$(iii)$ Autosomal $(2n+1)$

$A$: Turner's syndrome generally does not occur in males.
$R$: Foetus with $44 + YO$ complement generally dies.

Define aneuploidy. How is it different from polyploidy? Describe the individuals having the following chromosomal abnormalities:
$(a)$ Trisomy of $21^{st}$ chromosome
$(b)$ $XXY$
$(c)$ $XO$