The Consequences Of Unrepaired Dna Damage

Cells have evolved several ways to deal with damaged DNA, because it happens so often and can be so deadly. The first line of defense is DNA repair, but sometimes that fails. Next, the body tries to deal with DNA damage at the level of the cell. Cells with damage can be made to go quietly dormant while still holding their place in the body, or can be ordered to destroy themselves. If both these options fail, DNA damage can lead to birth defects or cancer. Senescence In general, cells lose their ability to divide, and thus reproduce, after about fifty divisions. This is called cellular senescence. However, if the DNA of cells becomes damaged, they may stop dividing far earlier. Cells that are exposed to toxins or trauma that damages their DNA are hazardous. If they reproduce, they may spread their defects in ways that could be dangerous to the entire organism. Therefore, some cells are induced to enter senescence early. This is replicative senescence. These cells still hold their place in the body, but do not divide. They are not dead or dying, and in fact are resistant to programmed cell death, or apoptosis. Apoptosis Apoptosis is cell suicide. It is also called programmed cell death, because it is a planned, orderly demise, which does minimum damage to surrounding cells. In essence, when a cell’s DNA is damaged beyond repair, or when the cell’s death is required for the whole body to work properly, the cell commits suicide. A child’s brain development and a woman’s menstruation both require apoptosis. In apoptosis, the organism withdraws positive signals that induce the cells to live, and the cell receives negative signals that encourage the cell to die. Positive signals might be growth factors. Negative signals might include ionizing radiation, some kinds of chemotherapy, or a Tumor Necrosis Factor or other type of messenger molecule from the immune system. The messenger orders the cell to begin to die. The cell may die in one of several ways. One pathway begins internally, when mitochondria, energy-producing organelles within cells, begin the destruction. Another pathway begins with an external signal that the cell should suicide. In both these cases, the cells cut up their own proteins, leaving debris, which is cleaned up by phagocytes, scavenger cells from the immune system. Neural cells can die another way. Apoptosis inducing factor, already in the intermembrane space of the mitochondria, is released, and binds to and Category:Home › Other • Pomegranates: A newly discovered superfood • Where did the joke why did the chicken cross the road come from and why is it funny? • Can mothers diagnosed with bipolar disorder make good parents? • Spiritual evolution of human consciousness • Tips for getting a college basketball scholarship • Living with Pseudotumor cerebri (PTC) • Caring for the caregiver • Technologys impact on society