Lecture 16 - Cancer Genetics Flashcards Preview

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Flashcards in Lecture 16 - Cancer Genetics Deck (41)
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1

Most common cancer causing death in men and women?

Lungs

2

Why have male death rates due to stomach cancer been dropping?

Increasing and proper use of refrigeration and less fermented foods in diet

3

How many oncogenes in human genome?

Over 100 known ones

4

Definition of oncogene?

Overexpressed or mutation activated proliferation gene causing cancer

5

What is a gain of function mutation?

Single mutation event converting proto-oncogenes into oncogenes

6

What is a loss of function mutation?

2 consecutive inactivating mutation events suppress/eliminate a tumor suppressor gene

7

What are 2 classifications of mutations that cause cancer? 2 names for each

Is each dominant or recessive?

1. Gain of function = overactivity mutation: dominant
2. Loss of function = underactivity mutation: recessive

8

What would be an example of a a gain of function mutation on Growth factor receptor?

Constitutive activation (always active regardless of whether the receptor is bound)

9

What would be an example of a a gain of function mutation on Growth factor receptor?

Constitutive activation (always active regardless of whether the receptor is bound)

10

What is the second mutation event a lot of the time in a loss of function mutation?

Loss of the second chromosome

11

What are the 4 types of accidents that can make a proto-oncogene overactive and convert it to an oncogene? What does each lead to?

1. Deletion or point mutation in coding sequence => hyperactive protein made in normal amounts
2. Regulatory mutation => normal protein overproduced
3. Gene amplification => normal protein overproduced
4. Chromosome rearrangement => nearby regulatory DNA sequence causes normal protein to be overproduced OR fusion of 2 genes to overproduce hyperactive protein

12

What kinds of proteins do most oncogenes code for? Provide 5 types and examples for each.

Proteins within growth and cell cycle pathways:
1. Growth factors: PDGF, EGF
2. Growth factor receptors
3. Intracellular signal transducers: GTP-binding proteins like Ras, RTKs
4. Cytoplasmic proteins: protein kinases, hormone receptors
5. Nuclear transcription factors

13

Can mutations enzymes in the glycolytic pathway lead to gain of function?

NOPE

14

What is a very common player in cancer?

v-ras = Harvey murine sarcoma virus (20% of cancers)

15

What is an experimental method to identify a human oncogene?

1. Extract human DNA from a cancerous cell
2. Insert the DNA in mouse cells and growth them
3. Extract one of the cell that transforms and clone it separately
4. Extract the DNA from these cells
5. Create a phage library with the DNA and probe it with the human DNA you had used to screen it

16

What cascade contains many proto-oncogenes? How does it work

MAPK cascase

Mutations at all levels can cause cancer AND ERK-mediated transcription can result in the upregulation of EGFR ligands (epidermal growtg factor receptor), such as TGF (transforming GF), thus creating an autocrine positive feedback loop that is critical for Ras-mediated cancers

17

What cancers are heritable?

Cancers caused by germline mutations

18

What cancers are nonheritable?

Cancers caused by somatic mutations

19

What are driver mutations?

Cancer mutations that are causally implicated in oncogenesis by conferring a growth advantage to the cancer cell

20

What are passenger mutations?

Cancer mutations that have NOT conferred clonal growth advantage to the cell and have NOT contributed to cancer development but are within cancer genomes as inert somatic mutations and are present in the final cancer

21

Describe the timing of somatic mutations acquired by a cancer cell and the processes that contribute to them.

1. Fertilized egg to adulthood: intrinsic mutation processes and environmental/lifestyle exposures lead to many passenger mutations
2. Early clonal expansion and benign tumor due to intrinsic mutation processes and environmental/lifestyle exposures causing driver mutations
3. Early-late invasive cancer due to mutator phenotype
4. Chemotherapy resistant recurrence due to chemotherapy

22

What is the Warburg effect?

Loss of p53 in cancer cells leads to them preferring to undergo anaerobic glucose metabolism by converting pyruvate to lactate even in the presence of oxygen => growth advantage because they have 3 C products available to build many other macromolecules compared to CO2 which they cannot use

23

Describe the 3 characteristics of autosomal dominant inheritance.

1. Each child has a 50% chance of inheriting the gene
2. No skipped generations
3. Equally transmitted by men and women

24

Describe the 3 characteristics of autosomal recessive inheritance.

1. Need 2 germline mutations (one from each parent) to develop the disease
2. Equally transmitted by men and women
3. NEVER 3 consecutive generations affected

25

What does gene penetrance mean? How is it expressed?

Fraction of those with the gene that express the trait by showing signs or symptoms of disease = ALL OR NOTHING

Expressed as a frequency at different ages

26

What does incomplete penetrance mean?

It means that the frequency of expression of the phenotype for those who have the gene is less than 100%

27

What 2 factors affect simple Mandelian inheritance patterns?

1. Penetrance
2. Expressivity

28

What are 2 examples of 2 oncogenes with incomplete penetrance?

BRCA1 and 2

29

What kind of penetrance do autosomal dominant diseases exhibit?

Reduced penetrance

30

What kind of penetrance do autosomal recessive diseases exhibit?

Complete penetrance