AP BIOLOGY

Detailed explanation-1: -If the DNA can be repaired, p53 activates other genes to fix the damage. If the DNA cannot be repaired, this protein prevents the cell from dividing and signals it to undergo apoptosis. By stopping cells with mutated or damaged DNA from dividing, p53 helps prevent the development of tumors.

Detailed explanation-2: -In normal cells, the p53 protein level is low. DNA damage and other stress signals may trigger the increase of p53 proteins, which have three major functions: growth arrest, DNA repair and apoptosis (cell death). The growth arrest stops the progression of cell cycle, preventing replication of damaged DNA.

Detailed explanation-3: -Activation of p53 in response to DNA damage is associated with a rapid increase in its levels and with an increased ability of p53 to bind DNA and mediate transcriptional activation. This then leads to the activation of a number of genes whose products trigger cell-cycle arrest, apoptosis, or DNA repair.

Detailed explanation-4: -A gene that makes a protein that is found inside the nucleus of cells and plays a key role in controlling cell division and cell death. Mutations (changes) in the p53 gene may cause cancer cells to grow and spread in the body.

Detailed explanation-5: -The experiments revealed that p53 plays an important role during DNA replication. When p53 is ‘healthy’, it binds to the replication fork. This ensures that replication restarts properly after it has passed faulty patches of the DNA. The p53 protein also helps to organize the proteins involved in DNA replication.