Question

The following pedigree chart is regarding a particular Mendelian disorder. Select the correct option regarding the disorder and genotype of the particular individual taken into consideration?
[0.7 mark]

• A. Colour blindness; $F_2\left(III\right)–X^{C}XorXX$
• B. Sickle cell anaemia; $F_1\left(V\right)–Aa$
• C. Haemophilia; $F_1\left(VI\right)–X^h{X}^h$
• D. Phenylketonuria; $F_1\left(II\right)–AaorAA$

Answer 1

The correct option is B Sickle cell anaemia; $F_1\left(V\right)–Aa$

The disorder cannot be X-linked because the girl child in $F_2$ (IV) is affected but her father is normal. Similar case is seen for the child $F_2\left(I\right)$.

If we consider the parents $F_1(I,II)$ which are unaffected, one of their children is affected. So, the character should be autosomal recessive and the parents of this children are heterozygous.
For the affected child $F_2\left(IV\right)$, her father should be heterozygous. In this way the considered disorder can be sickle cell anaemia and $F_1\left(V\right)$ would be heterozygous that is Aa. Hence. correct option is b.