Developoment and Differentiation

Differentiation

     Differentiation is the process by which the unspecialised embryonic cells change in structure and function during development and growth of an organism to form specialised cell types, tissues, and organs, distinct from one another. Differentiation makes cells of the same genotype to assume different phenotypes.

Molecular Basis of Differentiation

     Development involves precisely coordinated series of events. Each gene is switched on in its turn, and then something resulting from the expression of that gene, or some environmental influence, switches on the next gene in the programme.

Oncogenes

     Growth and division of normal cells are regulated by control mechanisms. One such control mechanism is contact inhibition. As a result of multiplication, the cells become crowded and come in contact with one another. This surface contact checks movement and division of cells. Therefore, the genes which control these processes are turned off. In the case of cancer cells, the mechanism of contact inhibition does not function. The cells continue to divide, forming a tissue mass called tumour. The cancer cells may invade other tissues and cause tumours in them also. Thus, cancer is a differentiation related disease.

Tumor Suppressor Genes

     They normally suppress the tumour formation and therefore the disease appears only when the active gene is lacking or both the alleles are lost.

Summary

     Every multicelluar organism begins its life as a single cell called zygote which by cleavage forms numerous identical cells. As development proceeds, these cells become specialised into components of various tissues and organs.