The monosomic condition in human beings depicted as $XO$ is referred to as

Read the following statements and choose the correct set of statements :
$(a)$ In sickle cell anaemia the mutant haemoglobin molecule undergoes polymerisation under high oxygen tension
$(b)$ Thalassemia is a qualitative problem
$(c)$ Turner's syndrome,Klinefelter's syndrome are common examples of chromosomal disorders.
$(d)$ Haemophilia is a sex-linked recessive disease

What is Down's syndrome? Give its symptoms and cause. Why is it that the chances of having a child with Down's syndrome increase if the age of the mother exceeds forty years?

What is the chromosomal constitution in Klinefelter syndrome due to trisomy?

Down syndrome is caused by an extra chromosome in the $21$st pair. What percentage of offspring from an affected mother and a normal father will show the effect of this disorder (in $\%$)?

$A$ man having Klinefelter's syndrome is