AP BIOLOGY

Detailed explanation-1: -Cancer is one of the scenarios where too little apoptosis occurs, resulting in malignant cells that will not die. The mechanism of apoptosis is complex and involves many pathways.

Detailed explanation-2: -In normal proliferating cells, initiation of these processes is controlled by genetically-defined pathways known as checkpoints. Tumors often acquire mutations that disable checkpoints and cancer cells can therefore progress unimpeded into S-phase, through G2 and into mitosis with chromosomal DNA damage.

Detailed explanation-3: -If the checkpoint mechanisms detect problems with the DNA, the cell cycle is halted, and the cell attempts to either complete DNA replication or repair the damaged DNA. If the damage is irreparable, the cell may undergo apoptosis, or programmed cell death 2.

Detailed explanation-4: -Cancer cells also fail to undergo programmed cell death, or apoptosis, under conditions when normal cells would (e.g., due to DNA damage). In addition, emerging research shows that cancer cells may undergo metabolic changes that support increased cell growth and division 5start superscript, 5, end superscript.