AP BIOLOGY

Detailed explanation-1: -A series of mutations in a cell causes it to proliferate more than its immediate neighbors. As the cluster of dividing cells grows over time, further mutations turn atypical hyperplasia into a cancer (carcinoma).

Detailed explanation-2: -Overexpression of growth factors or a lack of suppressor proteins can lead to rapid uncontrolled cell division. As cells proliferate without regulation, tumors occur that can become deadly if not treated.

Detailed explanation-3: -DNA Synthesis (S phase) In many cancer cells the number of chromosomes is altered so that there are either too many or too few chromosomes in the cells. These cells are said to be aneuploid. Errors may occur during the DNA replication resulting in mutations and possibly the development of cancer.

Detailed explanation-4: -This is called metastasis. 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-5: -Carcinogenesis can be divided conceptually into four steps: tumor initiation, tumor promotion, malignant conversion, and tumor progression (Figure 17-1). The distinction between initiation and promotion was recognized through studies involving both viruses and chemical carcinogens.