What does the nucleolu do?

Answer 1

The nucleolus directs the assembly of proteins within the cell nucleus. The nucleolus is the part of the nucleus containing most of the genes that code for the synthesis of ribosomal RNA (rRNA: the RNA molecules found in ribosomes).

Answer 2

rRNA molecules are assembled, together with many protein molecules into two subunits of future ribosomes. The subunits leave the nucleus through pores in the nuclear membrane, and enter the cytoplasm.

In the cytoplasm, the two ribosome subunits are brought together to form a functional ribosome at an early stage in translation, and separate again when the ribosome has fully translated a molecule of messenger RNA (mRNA).