Question

Describe the process by which a cell becomes cancerous. Include: The difference between benign and malignant tumors The two types of genes that can lead to development of cancer (and differences between them) and an example for each type that we discussed in class Reasons why cancer rates are higher in most counties in Maine than the US average.

Answer 1

• There are cell cycle checkpoints. It is a stage in the cell cycle where the cell examines internal and external factors and then "decides" if division should occur. The checkpoints are:

1. The G1 checkpoint

2.The G2 Checkpoint

3. The spindle checkpoint (transition metaphase- anaphase).

At G1 a cell checks for- Size, Nutrients, DNA status.

At G2, a cell checks for DNA replication

At spindle checkpoint, the sister chromatids attachment to the spindle is checked. All the sister chromatids must be attached to the spindle fibres.

• A cancer cell fails to pass any one of the above states and becomes immortal
• It also loses contact inhibition, a property that helps to maintain tissue balance in the body.

Benign Tumors remain localised at the place of their origin, gradually when they grow in mass, they start to spread by blood vessels by rupturing them. Thus, have a property called metastasis, after this, the tumor cells reach new places in the body and the tumor is said to malignant tumor or cancer.

The two genes that participate in cancer are Tumor suppressor genes and Oncogenes.

• A most important difference between tumor suppressor genes (TSG) and oncogenes is that tumor suppressor genes cause cancer if are inactivated (turned off) and oncogenes are known to cause cancer as a result of activation (turning on) of proto-oncogenes.
• TSG examples- BRCA1, BRAC2
• Oncogenes examples- myc gene, ras protein.

Cancer is more common in many countries compared to other because of life style, more of meat eating habits, smoking and drinking.