lecture 9 - cancer genetics

Question 1

What is cancer?

Answer 1

All cancers derive from single cells that have acquired the characteristics of continually dividing in an unrestrained manner and invading surrounding tissues.

Cancer cells behave abnormally due to changes in the DNA sequence of key genes, known as cancer genes.

Question 2

What percentage of people in the Western world develop cancer?

Answer 2

One in three people

This statistic highlights the prevalence of cancer in the population.

Question 3

What is the approximate number of cancer types?

Answer 3

Approximately 200 types

Each type has different causes, symptoms, and treatments.

Question 4

What factors influence an individual’s risk of developing cancer?

Answer 4

Age, lifestyle, and genetic make-up

These are key elements that can increase or decrease cancer risk.

Question 5

What is a mutation?

Answer 5

A change in the DNA sequence

There are two types: germline mutations and somatic mutations.

Question 6

What is a germline mutation?

Answer 6

A change in the DNA sequence that can be inherited from either parent

This type of mutation can be passed on to offspring.

Question 7

What is a somatic mutation?

Answer 7

A change in the DNA sequence in cells other than sperm or egg

These mutations are not inherited but can lead to cancer.

Question 8

What are cancer genes?

Answer 8

Genes causally implicated in oncogenesis

Mutations in these genes can occur somatically or be inherited.

Question 9

What are the two types of cancer genes?

Answer 9

Tumour suppressor genes and Oncogenes

These play different roles in cell growth and division.

Question 10

What is the function of tumour suppressor genes?

Answer 10

To PREVENT cell growth/division

They act as a check on cell proliferation.

Question 11

What is the function of oncogenes?

Answer 11

To PROMOTE cell growth/division in a controlled manner

When mutated, they can lead to uncontrolled growth.

Question 12

Give examples of mutation types.

Answer 12

• Substitution
• Deletion
• Insertion
• Inversion
• Duplication

These mutations can affect the function of genes.

Question 13

What are the stages of cancer progression?

Answer 13

• Benign Tumour
• In situ cancer
• Invasive cancer
• Metastatic cancer

Understanding these stages is crucial for diagnosis and treatment.

Question 14

Name external causes of cancer.

Answer 14

• Ultraviolet radiation
• Tobacco smoke
• Lifestyle factor: diet
• Biological factor: virus (HPV and cervical cancer)

These factors can increase the likelihood of developing cancer.

Question 15

What is the KRAS gene responsible for?

Answer 15

It codes for a signalling molecule

Mutations in this gene are found in many cancers, including pancreatic cancer.

Question 16

What do heterozygous mutations indicate?

Answer 16

A double peak indicates a mutation on one chromosome and not the other

This can provide insights into cancer genetics.

Question 17

What are significant KRAS mutations?

Answer 17

• Amino acids 12
• 13
• 61
• 146

These mutations are commonly associated with various cancers.

Question 18

What is the role of KRAS in cellular signaling?

Answer 18

Helps transmit external growth signals to the cell nucleus

It is activated by GTP and inactivated when GTP is hydrolyzed to GDP.

Question 19

What is the hereditary component percentage in cancer cases?

Answer 19

Only 5–10% of cancer cases have a clear hereditary component

Examples include BRCA1 and BRCA2 in breast cancer.