Cell Differentiation

Multicellular organisms have a wide variety of cells, all ultimately derived from the zygote in sexually reproducing forms. These cells differ in shaper and function. Glands cells are specialized for secretion, muscle cells for contraction and nerve cells for conduction. The early stages of development have relatively similar cells. The process by which cells gradually specialize and undergo change in shape and function is called cell differentiation. Differentiation of cells begins during gastrulation and continues through tissue formation. After the cells become well differentiated they cannot go back to the undifferentiated form.

It must be remembered that though the cells of an individual vary greatly, they are identical as far as their genes are concerned. The DNA molecules are identical in all the cells, since they have been derived from the DNA molecules of the zygote. The problem of cell differentiation therefore is: how can an identical genetic complement give rise to such a wide variety of structure and function? In other words, how can one cellular genotype result in so many different cellular phenotypes?

The nucleus and the cytoplasm have mutual control over each other and are, therefore, interdependent. The cytoplasm with its ribosomes is the site of protein synthesis and provides energy to the cell. Nuclear DNA provides the template for the synthesis of messenger RNA. A discussion on cell differentiation should therefore consider how the nucleus controls the cytoplasm, and conversely, how the cytoplasm controls and nucleus. Differentiation results from the interaction of the nucleus and the cytoplasm.