Select the incorrect statement from the following.

How many types of zygotic combinations are possible between a cross $Aa \; BB \; Cc \; Dd \times AA \; bb \; Cc \; DD$?

Haemolytic jaundice is caused due to a dominant gene but only $10\%$ of the people who carry the gene actually develop the disease. $A$ heterozygous man marries a homozygous normal woman; what proportion of the children would be expected to develop the haemolytic disease?

Dominant epistasis is shown by

It is said that harmful alleles are eliminated from a population over a period of time,yet sickle cell anaemia persists in the human population. Why?

Choose the correct option for the given descriptions:
$(i)$ The heterozygous female transmits the disease to the son.
$(ii)$ Change in the shape of the $RBC$ from biconcave disc to elongated sickle-like structure.
$(iii)$ Mentally retarded.
$(iv)$ Haemoglobin is not formed in the proper amount in the blood.