AP BIOLOGY

Detailed explanation-1: -Disruption of the normal regulation of cell-cycle progression and division are important events in the development of cancer. Complex networks of regulatory factors respond to the tumor microenvironment and stress signals, such as those resulting from damaged DNA, dictate whether cells proliferate or die.

Detailed explanation-2: -Mutation in proto-oncogenes produces oncogenes that cause loss of control over cell cycle and uncontrolled and repetitive entry of cell in cell cycle thereby forming tumors. This makes option A incorrect.

Detailed explanation-3: -Cancer cells have mutated genes and are less specialized than normal cells. Cancer cells don’t follow the regular routine. Needed or not, they grow and divide and don’t die off when they should. It’s this out-of-control growth that leads to cancer.

Detailed explanation-4: -So, the correct answer is ‘They show contact inhibition’.