So that genetic information can reach all organelles in the cell easily. The nucleus of animal cells contain DNA, which codes for different polypeptides (the components of proteins). This code is copied and sent to ribosomes (the polypeptide synthesising organelle in the cell) in the form of mRNA. read more
The location of the nucleus can vary, depending on the type of the cell. The usual location of the nucleus is at the centre (animal cells), but it can also be at the periphery (plant cells). The reason for that is the vacuole that takes the central position in the plant cell. read more