Lecture 9: Oncogenes

What are oncogenes?

Genes whose presence contributes to uncontrolled cell proliferation.

What are tumor suppressor genes?

Genes whose absence or inactivation contributes to uncontrolled cell proliferation.

What is a proto-oncogene?

A normal host gene that can be modified into an oncogene.

What is the process called when a proto-oncogene is modified?

Gain-of-function.

What are the sources of oncogenes?

New genetic material introduced into the genome (e.g., viruses) or modification of existing genetic material.

What is a point mutation?

A change in a base pair that alters the resulting protein.

What is gene amplification?

The creation of multiple copies of the same gene, leading to overproduction of the resulting protein.

What is chromosomal translocation?

A piece of one chromosome is attached to another chromosome.

What is insertional mutagenesis?

The insertion of a piece of foreign gene near a normal gene, which can lead to over-promotion of gene transcription.

What is the function of oncogenes?

They modify signaling pathways, self-produce growth factors, modify receptors, act as transcription factors, and regulate the cell cycle or cell death.

What is the role of Bcl2 in cancer?

It inhibits apoptosis, allowing cells to survive despite damage.

How many tumor suppressor genes are there in the human body?

Only a few dozen out of 25,000 genes.

What is loss of heterozygosity?

A condition where one copy of a tumor suppressor gene is mutated, leading to the loss of function of the other copy during cell division.

What is the most commonly mutated tumor suppressor gene in human cancers?

P53.

What is the gatekeeper function of P53?

It can arrest the cell cycle and induce apoptosis in cells with DNA damage.

What happens when P53 is dysfunctional?

Cells with severe DNA damage may continue to proliferate.

What role do DNA repair enzymes play in cancer?

They help maintain DNA stability and prevent mutations that can lead to cancer.

What is the relationship between tumor suppressors and familial cancer syndromes?

Tumor suppressors were initially identified in familial cancer syndromes.

What can trigger loss of heterozygosity?

Several factors during cell division can lead to loss of heterozygosity.

What is the significance of mitotic spindle behavior proteins?

They are involved in maintaining DNA stability and preventing cancerous growth.