In man, four phenotypes of blood groups are due to the presence of antigen-$A$ and antigen-$B$ on the $RBC.$ The chromosome that has the gene to control these antigens is
$X$-chromosome
$21^{\text {st }}$ chromosome
$9^{\text {th }}$ chromosome
$7^{\text {th }}$ chromosome
Frequency of Down’s syndrome increases when the maternal age is
In which of the following disorder a single protein that is a part of the cascade of proteins involved in blood clotting is affected?
A pedigree chart below shows the inheritance of a particular sex-linked trait ("trait") Key: Unaffected Males Affected Males Unaffected Females Affected Females How is the trait being studied in the pedigree chart above?
One of the following is sex-influenced character
Extranuclear inheritance is a consequence of presence of genes in