20. Cancer Genetics

Question 1

How do most people get cancer?

Answer 1

Acquired from the environment. NOT inherited through genetics.

Question 2

Explain Knudson’s Two Hit Model on Retinoblastoma.

Answer 2

Bilateral retinoblastoma runs in families. Unilateral appears sporadically.

Question 3

Name the 3 classes of cancer genes.

Answer 3

1. Tumor Supressor Genes
2. Oncogenes
3. DNA repair genes

Question 4

For inherited forms of cancer, what exactly do you inherit from your parents?

Answer 4

The predisposition to cancer, NOT the cancer itself.

Question 5

Characteristic of chromosomes seen in gene mapping that can act as a marker for detecting cancer.

Answer 5

Loss of Heterozygosity

Question 6

Enzyme that can cause immortal cells if it is always active.

Answer 6

Telomerase

Question 7

Disesase and mutated gene that leads to a patient having cafe au lait spots and skin tumors.

Answer 7

1. Neurofibromatosis

2. Mutation in tumor suppressor gene NF-1 which activates a GTPase which inactivates Ras

Question 8

p53 binds to the promoter region of the gene that codes for p21. What is the promotor region called?

Answer 8

CDK1A

Question 9

Protein that inhibits cyclin and cyclin dependent kinase which inhibits the cell cycle.

Answer 9

p21

Question 10

Protein that signals another protein MDMA to attach ubiquitin to p53 and have it degraded.

Answer 10

p14

Question 11

Disorder characterized by an inhereted mutation in p53.

Answer 11

Li-Faumeni Syndrome

Question 12

Disorder from a mutation in APC where patients have many polyps in the colon.

Answer 12

Familial Adenomatous Polyposis Coli

Question 13

Disorder from a mutation in MSH1 and MLH2 genes where patients have few polyps in the colon.

Answer 13

Hereditary Non-polyposis Colon Cancer (DNA mismatch repair malfunction)

Question 14

Explain the multi-step model leading to colon cancers. (4 steps)

Answer 14

1. Mutation in APC - no cell to cell contact growth inhibition (beta-catenin)
2. K-Ras activation - gain of function
3. TP53 mutation - no p53 expression
4. Other genes altered like SMAD4 - metastasis

Question 15

Mutation in this gene leads to increased risk of breast cancer in men.

Answer 15

BRCA2

Question 16

What is the function of BRCA1 in preventing breast cancers?

Answer 16

Binds BRCA2 and RAD51 so that double stranded DNA breaks can be repaired.

Question 17

Name two main causes for familial melanomas.

Answer 17

1. Mutation in p16: a CDK inhibitor

2. Mutation in CDK4: gain of function mutation