Heterosis is . . . . . . .

$A$ conducting rod of length $\ell$ is moving with velocity $v$ in a uniform magnetic field $B$ directed into the plane of the paper,as shown in the diagram. Which end of the rod is at a lower potential?

In humans,which disorder is caused due to the absence of one of the $X$ chromosomes,i.e.,$45$ chromosomes with $XO$ genotype?

Calcium is obtained by which of the following methods?

What do mast cells secrete?

Heating $(NH_4)_2Cr_2O_7$ liberates a gas. The same gas is obtained by: