Which mammals have more yolk than cytoplasm in their eggs?

Tjio and Levan's contribution is very significant because they

Which of the following statements are correct?
$i$. $X$ chromosome has a large amount of euchromatin.
$ii$. Heterochromatin is genetically inert.
$iii$. Both $X$ and $Y$ chromosomes are homologous.
$iv$. Crossing over does not take place in sex chromosomes in females.
Choose the correct option.

What percentage of genes does a child receive from his father?

Which of the following is $NOT$ true for $Drosophila$ $melanogaster$?

Genes that are similar in phenotypic effect when present separately,but together interact to produce a different trait and the ratio is $9:7$ in the $F_2$ generation. What are such genes known as?