AP BIOLOGY

Detailed explanation-1: -If a cell can not stop dividing when it is supposed to stop, this can lead to a disease called cancer. Some cells, like skin cells, are constantly dividing. We need to continuously make new skin cells to replace the skin cells we lose.

Detailed explanation-2: -When aging cells stop dividing, they become “senescent.” Scientists believe one factor that causes senescence is the length of a cell’s telomeres, or protective caps on the end of chromosomes. Every time chromosomes reproduce, telomeres get shorter. As telomeres dwindle, cell division stops altogether.

Detailed explanation-3: -Cancer is a disease caused when cells divide uncontrollably and spread into surrounding tissues. Cancer is caused by changes to DNA. Most cancer-causing DNA changes occur in sections of DNA called genes. These changes are also called genetic changes.

Detailed explanation-4: -Usually, we have just the right number of each type of cell. This is because cells produce signals to control how much and how often the cells divide. If any of these signals are faulty or missing, cells might start to grow and multiply too much and form a lump called a tumour.