In the given figure,which substance is synthesized by the part labeled $A$?

Which of the following are used to define the karyotype of a species?
$1$. The number of chromosomes
$2$. The chromosome length
$3$. The positions of the centromeres

Genes are located in.....

The controlling centre of the cell is:

Explain why the nucleus is considered the central point of all activities of the cell.

What is the function of nuclear pores?