Question

1. If an individual receives an overdose of radiation, the two areas that suffer the most damage are the blood and the intestines. Symptoms include a decreased blood cell count and gastrointestinal upset. The bone marrow (blood) and the lining of the intestines are the two most rapidly dividing areas of the body. Indicate how these two facts might be related.

2. In your own words, identify and explain the purposes of cell division.

Answer 1

•We know that cell is going to different phases in its life cycle as – G1-S-G2- M, with the help of CDK and Cyclins protein.

•This regulate the cell division process in our body. We know that in bone marrow and intestinal lining , there is a continuous formation of new cells [means cell division is going on ].

•If there is a damage or disruption in normal cell cycle , the normal cell undergoes the apoptosis condition [programmed cell death]

•Now let us focus on effect of radiation on cell cycle.

•When cells are exposed to ionizing radiation, they initiate a complex response that includes the arrest of cell cycle progression in G1 and G2, apoptosis and DNA repair.

•DNA is an important subcellular target of ionizing radiation, but oxydative damage to plasma membrane lipids initiates signal transduction pathways that activate apoptosis and that may play a role in cell cycle regulation.

•The ataxia telangectasia mutant (ATM) protein and/or the DNA-dependent protein kinase (DNA-PK), that are both activated by DNA damage, may initiate cell cycle arrest by activating the p53 tumor suppressor protein.

• The p53 protein acts as a transcription factor and regulates expression of several components implicated in pathways that regulate cell cycle progression.

•The best known, p21WAF1/CIP1 protein, is an inhibitor of cyclin-dependent kinases (CDK) , it is most effective toward G1/S cyclins and arrest G1 phase.

• Moreover, radiation-induced G2 arrest was shown to require inhibitory phosphorylation of the kinase cdc2 via an ATM-dependent pathway.

•In short we see that it disrupt the steps of cell cycle . But here as the normal cell, no apoptosis process.

•So the haematopoetic cells are not divide itself and so the intestinal cells . Which may result in lack of blood cells formation or may trigger the cancer by uncontrolled cell division and same with intestinal level.