The condition of sex chromosomes in a male child with Down's syndrome will be:

Choose the correct answer regarding the following statements:
$(i)$ Sickle-cell anaemia is controlled by three pairs of alleles.
$(ii)$ Trisomy is a chromosomal disorder.
$(iii)$ $47$ chromosomes are present in a person having Turner's syndrome.

Down syndrome is caused by an extra copy of chromosome $21$. If an affected mother and a normal father produce offspring,what percentage of the offspring will be affected by this disorder (in $\%$)?

The given figure represents which disorder?

When one or more genes are missing from the middle part of a chromosome,it is called:

In a diploid organism,the formation of a multivalent during meiosis is due to: