Polydactyly in humans is due to:

Which of the following is not a hereditary disease?

In sickle-cell anaemia,which of the following amino acids is substituted?

Haemophilia is a type of genetic disorder that is:

Identify the given figure and select the correct option for $P, Q, R$ and $S$.
$\quad P \quad Q \quad R \quad S$

$A$ woman with normal vision marries a man with normal vision and gives birth to a color-blind son. Her husband dies,and she remarries a color-blind man. What is the probability of color blindness in her children from the second marriage?