Question

In humans, attached earlobes are a dominant feature over free earlobes while hypertrichosis of the ear is a holandric (Y-linked) feature. A man with attached earlobes and extensive hair on pinna married a woman having free earlobes. The couple had one son with attached earlobes and hairy pinna, another son with free earlobes and hairy pinna and two daughters with attached earlobes. One of the daughters married a man with free earlobes and sparse hair on pinna. They had two Sons. What would be the characteristics of their pinnae?
A)Both will have attached earlobes and sparse hair on pinna.
B)There would be equal chances for both having free or attached earlobes and sparse hair on the pinnae.
C)They would have hairy pinnae and there would be 1 in 8 chances that both will have attached earlobes.
D)Both will have free earlobes and extensive hair on pinnae.

Answer 1

Hint: Holandric gene inheritance is the inheritance of Y-linked genes. In human beings males have Y genes represented as (XY). So the Y linked genes will be passed from father to son. The daughters will not have any effect of this gene.

Complete answer:
According to the question, the cross is made in between the attached earlobe ( XaYah) and normal one (XX). Where the attached earlobe is dominant.
The offspring would be XaYh X X

	Xa	Yh
X	XaX ( daughter with attached lobe)	XYh ( son withfree lobe with hairy pinna)

If the daughter marries the man with free earlobe then
Female (XaX) is crossed between male with free earlobe sparse pinna (XY)

	X	Y
Xa	XaX (female attached lobe)	XaY(male attached lobe with sparse hair pinnae)
X	XX (free lobe female)	XY ( male free lobe with sparse hair pinna)

Both the sons will have sparse hair earlobe as it is a Y linked gene and the father can only transfer the gene to the son. If the father has hairy lobes then son will have hairy lobe. One son will have attached lobe and the other will have free lobe.

Hence, the correct answer is option (B)

Note: Hypertrichosis is also known as werewolf syndrome. It is a heritable condition in which hairs are developed all over the body or in isolated patches. There is no cure to this disease as it is inherited through genes. The Adrenal gland is responsible for hypertrichosis.