Biology Chapter 10: Genes and Cancer

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Questions and Answers

What is the main characteristic of cancer?

Programmed cell death and the inability of cells to grow

The inability of cells to divide

Uncontrolled cell growth and the ability of cells to spread (correct)

The ability of cells to repair damaged DNA

What is the leading cause of death in developed countries?

Cancer (correct)

Hypertension

Diabetes

Heart disease

What percentage of tumors have a mutation in the p53 gene?

50%

90-100%

It varies depending on the type of cancer (correct)

70-90%

What is the role of the RB1 gene?

To stop cell growth Signup and view all the answers

What is the result of mutated BRCA1 or BRCA2 genes?

Increased risk of breast and ovarian cancer Signup and view all the answers

What is the goal of personalized medicine in cancer therapy?

To target specific oncogenes in cancer cells Signup and view all the answers

What is the name of the protein produced by the BCR-ABL hybrid gene?

It is not specified in the text Signup and view all the answers

What is the role of the Ras protein?

To relay messages as a signal transducer Signup and view all the answers

What percentage of colon cancer is associated with Hereditary Nonpolyposis Colon Cancer (HNPCC)?

It is not specified in the text Signup and view all the answers

What is the result of a mismatch repair deficiency?

Genomic instability Signup and view all the answers

What is the name of the gene that is often mutated in Chronic Myelogenous Leukaemia (CML)?

C-ABL Signup and view all the answers

What is the name of the condition where multiple polyps grow in the large intestine?

Familial Adenomatous Polyposis (FAP) Signup and view all the answers

What is the name of the drug that targets the BCR-ABL hybrid gene?

Gleevec Signup and view all the answers

What is the role of the APC gene?

To suppress tumour growth Signup and view all the answers

What is the result of a mutation in the K-RAS gene?

Uncontrolled cell growth Signup and view all the answers

What is the percentage of cancers associated with viruses?

15% Signup and view all the answers

What is the role of the p53 gene?

To trigger apoptosis Signup and view all the answers

What is the main effect of the viral E7 protein in cervical cancer?

It blocks pRB and increases cell division Signup and view all the answers

What is the estimated percentage of skin cancers caused by sunlight or tanning beds?

95-99% Signup and view all the answers

What is the name of the genes that are mutated in Hereditary Nonpolyposis Colon Cancer (HNPCC)?

MSH2 and MLH1 Signup and view all the answers

Study Notes

What is Cancer?

Cancer is a phenotype produced by the environment and a person's genotype.
It is a group of diseases affecting many different cells and tissues in the body.
Two main characteristics of cancer:
- Uncontrolled cell division.
- Ability of cells to spread (metastasis).

Causes of Cancer

Several different causes:
- Genetic predisposition.
- Mutagenic chemicals.
- Some viruses.
- Chromosomal changes.
- Environmental factors.
- Time.
Mutation is the starting point for all cancers.

Sporadic vs Familial Cancers

Most cancers are sporadic (accumulation of mutations over time).
Environmental factors can speed up the process.
At least two mutations are required.
Some cancers are familial (e.g., inherited breast cancer).
- These have helped identify cancer genes.
- Inherit one mutated gene, then the normal gene mutates too (Loss of Heterozygosity, LOH).

Inheritable Susceptibilities

Examples of inherited cancer genes:
- BRCA1 and BRCA2 (breast cancer).
- FAP1 (familial adenomatous polyposis).
- MSH2 (Lynch Syndrome I).
- LFS1 (Li-Fraumeni Syndrome).
- MEN1 (multiple endocrine neoplasia type I).

Progression of Cancer

All cancers start in a single cell.
Mutations accumulate over time until the cell becomes cancerous.
Once formed, cancer cells divide continuously.
Further mutations accumulate, making the cancer more aggressive.
Cancer cells become invasive and can colonize new areas.

Types of Cancer

Classified by:
- Tissue or organ of origin (e.g., carcinoma, sarcoma, leukaemia).
- Location (e.g., skin, lung, colon).

Cell Cycle Checkpoints

G1/S Checkpoint: checks internal and external conditions.
G2/M Checkpoint: checks that all DNA has been copied and any mistakes have been repaired.
M Checkpoint: checks that chromosomes are lined up correctly.

Tumour-Suppressor Genes and Oncogenes

Tumour-suppressor genes: decrease or stop cell division (e.g., RB1).
Oncogenes: drive cell division in response to signals received (e.g., Ras).

DNA Repair and Genome Stability

All cancers result in some form of genomic instability.
Aneuploidy, loss of chromosomes, duplications, deletions, inversions, etc.
Result from a loss of the ability to repair DNA damage.

Genes and Cancer

Examples of genes involved in cancer:
- Retinoblastoma (RB1).
- Ras.
- BRCA1 and BRCA2.
- p53.

BRCA1 and BRCA2 mutations account for 15-20% of hereditary breast cancers.
Associated with increased risk of breast, ovarian, and prostate cancer.

The Pathway to Colon Cancer

>6 mutations required to form cancer.
Genetic and environmental factors.
Mostly sporadic, ~5% inherited.

Familial Adenomatous Polyposis (FAP)

Accounts for ~1% of all colon cancers.
100% lifetime risk of developing colon cancer.
Associated with chromosomal instability.
Requires 5-7 mutations.
Order of mutations is important.

Hereditary Nonpolyposis Colon Cancer (HNPCC)

Mutations in 7 different genes lead to HNPCC.
Mutations in MSH2 and MLH1 cause 90%.
Associated with increased risk of colon, stomach, pancreas, endometrial, and ovarian cancer.

Chromosomal Rearrangement and Cancer

Several cancers are associated with translocations (e.g., Chronic Myelogenous Leukaemia (CML)).

Cancer is a Genomic Disease

Accumulation of mutations throughout the genome.
DNA sequencing, family studies, and GWAS are helping identify cancer-causing changes.

Better Identification of Cancer Genes

Genes in normal tissue can be compared to genes in cancerous tissue.
Identifies which mutations have occurred.

Epigenetics and Cancer

DNA and histone modifications can lead to cancer.
Allows cells to proceed through the cell cycle with damaged DNA.

Targeted Cancer Therapy

Affects only cancer cells.
Selectively blocks oncogenes and slows cell division.
Two types of drugs – small molecules and monoclonal antibodies.

Environmental Effects on Cancer

Viruses, chemicals, radiation, diet, smoking, sun exposure, etc. can all damage DNA.

Viruses and Cancer

15% of cancer associated with viruses.
Examples: HPV16 and HPV18 causing cervical cancer.

Other Environmental Agents

Smoking: 75-85% of smokers develop cancer.
Sun exposure: 95-99% of skin cancers.

Reducing Your Risks

Various ways to reduce the risk of cancer.

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Description

This quiz covers the basics of cancer, its characteristics, and the relationship between genotype and phenotype. It also discusses the impact of medical treatments on life expectancy and cancer risk.