One of the genes present exclusively on the $X$-chromosome in humans is concerned with
Baldness
Red-green colour blindness
Facial hair/moustaches in males
Night blindness
A person may have one gene for normal haemoglobin and one gene for sickle cell haemoglobin. This heterozygous condition is called
In the given pedigree, indicate whether the shaded symbols indicate dominant or recessive allele.
A couple whose sons are colourblind with $AB$ blood group, identify the parents from the following..