Barr bodies (seen in saliva test in Olympic games) are found in human and are associated with

Some individuals with blood group -$A$ may inherit the genes for blonde hair, while other individuals with blood group -$A$ may the gene for brown hair. This can be best explained by the principle of

The example of epistatic gene is shown by

Sex-linked characters are

Lesch Nyhan disease is an $X-$linked recessive disorder that causes neurological damage in human beings. $A$ survey of $500$ mates from a caucasion population revealed that $20$ were effected with this disorder. What is the frequency of the normal allele in this population?