In a cross between a male and female, both heterozygous for sickle cell anaemia gene, what percentage of the progeny will be diseased? (In $\%$)

Following characters are indicate

$(i)$ presence of sickle - shaped $RBC$

$(ii)$ Blood not clot, non stop bleeding

$(iii)$ The heterozygous female transmit the disease to sons.

$(iv)$ Both heterozygous parents transmit the disease to offspring

If a father and son are both defective in red-green colour vision, is it likely that the son inherited the trait from his father ? Comment.

Which one of the following symbols represents mating between relatives in human pedigree analysis?

Given below is a pedigree chart showing the inheritance of a certain sex- linked trait in humans.

The trait traced in the above pedigree chart is

The character of organisms is said to be sex linked when its gene is carried on