Frequency of Down’s syndrome increases when the maternal age is
Above $35$ years
Below $35$ years
During $1^{st}$ pregnancy
In mothers of at least $3$ children
Jumping genes in maize were discovered by
When a diploid female plant is crossed with a tetraploid male, the ploidy of endosperm cells in the resulting seed is
A hereditary disease which is never passed on from father to son is
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
Animal which remains male initially, then changes to female $(Tapeworm\, proglottides)$ is called