Colour blindness is caused due to

Absence of teeth,bifid tongue and mental retardness are observed in . . . . . . .

Which one of the following disorders is caused by the substitution of Glutamic acid (Glu) by Valine (Val) at the sixth position of the beta globin chain of the haemoglobin molecule?

Which of the following most appropriately describes haemophilia?

Which of the following abnormalities is due to an autosomal dominant mutation?

$A$ color-blind girl is rarely born. This occurs only when: