$A$ condition characterized by not having an exact number of chromosomes in a diploid set is called

In a human karyotype,if there are $45$ chromosomes with an $XO$ configuration,which disorder is present?

The reduction of one pair of chromosomes in humans is due to:

Match the Column $I$ with Column $II$:

Column $I$	Column $II$
$(A)$ Autosomal trisomy	$(i)$ Turner's Syndrome
$(B)$ Allosomal trisomy	$(ii)$ Mendelian disorder
$(C)$ Allosomal Monosomy	$(iii)$ Klinefelter's Syndrome
$(D)$ Cystic fibrosis	$(iv)$ Down's Syndrome

Three copies of chromosome-$21$ in a child with Down's syndrome have been analysed using molecular biology technology to detect any possible $DNA$ polymorphism with reference to different alleles located on chromosome-$21$. Results showed that out of $3$ copies,$2$ of the chromosomes of the child contain the same alleles as one of the mother's alleles. Based on this,when did the non-disjunction event most likely occur?

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