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POM GENETICS > Cancer Genetics > Flashcards

Cancer Genetics Flashcards

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1
Q

What is a cancer?

A

An abnormal growth of cells which tend to proliferate in an uncontrolled manner, and in some cases, to metastasize

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2
Q

What causes cancer cells to behave abnormally?

A

Changes in the DNA sequence of key genes which are known as cancer genes

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3
Q

What are the two causes for mutations in DNA?

A

Tumour supressor genes being silenced or oncogenes being over-expressed

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4
Q

What are oncogenes?

A

Genes which stimulate the cell cycle

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5
Q

What are tumour supressor genes?

A

Genes which halt the cell cycle

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6
Q

What are the 6 hallmarks of cancer?

A

SAAIIL

Self Sufficiency
Avoid apoptosis
Angiogenesis
Invasion and metastasis
Insensitive to anti-growth signals
Limitless division

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7
Q

What is a benign tumour?

A

A mass of well-differentiated cells that grows slowly, is capsulated and lacks the ability to invade neighbouring tissue or metastasise

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8
Q

What is a malignant tumour?

A

A tumour which is not self limited in growth, cells are poorly differentiated and capable of invading into adjacent tissues = metastasis

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9
Q

What four things can cause cancer?

A
  • Radiation
  • Chemicals
  • Viruses
  • Hereditary alteration in genes which make a person more susceptible to cancer
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10
Q

What is the difference between benign and malignant tumours?

A

benign grow slow, malignant fast
benign is well differentiated, malignant is not
benign is capsulated, malignant is not
benign cannot metastasize or invade neighbouring tissue, malignant can

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11
Q

What type of cancers have epithelial tissue origin?

A

Carcinomas

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12
Q

What are common types of carcinomas?

A

Lung, breast and colon cancer`

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13
Q

What is the name given to cancers which arise from cells found in the connective tissues of the body?

A

Sarcomas

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14
Q

What are cancers that arise in lymph nodes and tissues of the body’s immune system called?

A

Lymphomas

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15
Q

What are cancers that arise from immature blood cells that grow in the bone marrow called?

A

Leukaemia

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16
Q

What is the most common cancer in children?

A

Acute lymphoblastic leukaemia

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17
Q

What type of mutation can be passed on to off-spring?

A

Germline mutations can be passed on

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18
Q

What type of mutatins can’t be passed on to off-spring?

A

Somatic mutations

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19
Q

A gene change in which cells cause germline mutations?

A

Reproductive cells

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20
Q

What are somatic mutations also known as?

A

Acquired or sporadic mutations

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21
Q

What are the seven types of mutations?

A

deletions
insertions
aneuploidy
inversions
translocations
single base mutations
chromosome instability

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22
Q

What is a deletion mutation?

A

When one or more nucleotide is removed from the DNA

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23
Q

what is a duplication mutation?

A

When one or more copies of a gene or region of a chromosome are made

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24
Q

What is an inversion?

A

Reversing the orientation of a chromosomal segment

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25
Q

What is a driver mutation?

A

A mutation which contributes to cancer growth

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26
Q

What is a passenger mutation?

A

A mutation which occurs during cancer growth

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27
Q

What type of studies can help identify cancer germline mutations?

A

Positional cloning linkage studies through gene mapping and gene indentification

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28
Q

What are the three types of point mutations?

A

Silent, non-sense and mis-sense

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29
Q

What affect does UV radiation have on the DNA?

A

forms covalent bonds between two adjacent pyrimidines (C and T) in the DNA molecule which causes cross linking, resulting in the formation of a dimer

30
Q

What happens if the dimer formed due to UV radiation is not repaired?

A

Most DNA polymerases will insert 2 adenine opposite the dimer, resulting in a mutation

31
Q

What does oncogene issues generally result in?

A

An increase in some form of protein activity, or a loss of regulation

32
Q

Describe the process of multistep carcinogenesis?

A
  1. begins with mutation in tumour supressor gene which therefore allows excessive cell proliferation
  2. proliferating cells tend to acquire additional mutations
  3. overtime the accumulated damage can yield a malignant, metastatic tumour
33
Q

what type of protein is RAS?

A

A GTPase

34
Q

What state is RAS in when GDP is bound?

A

It is inactive

35
Q

Does Ras bind GDP or GTP with a higher affinity?

A

GTP

36
Q

When Ras binds GTP, what state is Ras then in?

A

Active state

37
Q

How does GAP ensure that Ras is not always active?

A

GTPase Activating protein hydrolyses the GTP into GDP so Ras is turned off

38
Q

What happens when RAS is constantly stuck in the active form?

A

the cell extensively proliferates causing cancer as RAS controls a lot of cellular signalling pathways

39
Q

What is the two hit hypothesis? and how does it relate to mutations to tumour supressor genes?

A

The two hit hypothesis states that both alleles that code for a particular protein must be affected before an affect is manifested.

Most mutations to tumour supressor genes are recessive, meaning in order for a particular cell to become cancerous, both of the alleles for the cells tumour supressor genes must be mutated

40
Q

What do mutations in tumour supressor genes result in?

A

A loss of function, as they can no longer stop the cell from proliferating uncontrollably

41
Q

what is the first event in the two hit hypothesis?

A

An inherited mutation - however inheriting one germ line copy of the damaged gene is not sufficient

42
Q

What is the second hit in the two hit hypothesis?

A

When the second (good) copy in the gene pair is mutated - causing cancer

43
Q

What is p53?

A

a tumour supressor protein that is encoded by the TP53 gene

44
Q

Loss of the TP53 gene gene due to mutation or deletion occurs in what percentage of human cancers?

A

> 50%

45
Q

What is Li-Fraumeni syndrome?

A

an inherited condition which is characterised by an increased risk for certain types of cancers

46
Q

What mutagens can cause damage to the TP53 gene?

A

Chemicals, radiation or viruses

47
Q

What is a retinoblastoma?

A

Cancer of the retina

48
Q

What does Rb protein do?

A

Prevents excessive cell growth by inhibiting cell cycle progression until a cell has made all the necessary checks in the G1 phase

49
Q

What transcription factor does retinoblastoma protein bind?

A

E2F

50
Q

What has to happen to the Rb for the E2F to be released?

A

Rb has to be phosphorylated - this leads to transcription

51
Q

How do cancer cells evade the immune response?

A

activation of the checkpoint pathways such as PD-1 send negative signals to the cell to stop if from attacking the tumour cell

52
Q

how does nivolumab work?

A

binds to the PD-1 receptor and blocks its interaction with PD-L1 and PD-L2,so the negative signals cannot be sent anymore

53
Q

What is positional cloning?

A

A lab technique used to locate the position of a disease associated gene along a chromosome

54
Q

Which type of mutation tends to cause clonal expansions?

A

Driver mutations

55
Q

What is the life-time risk of developing cancer in a particular tissues correlated with?

A

How often the stem cells in that tissue divide

56
Q

How are most cancer causing mutations involving oncogenes acquired?

A

Chromosome rearrangements and gene duplications

57
Q

What does the translocation between chromosome 9 and 22 result in?

A

The formation of the ABL-BCR gene which makes elevated tyrosine kinase activity - leads to more cell proliferation

58
Q

What is a proto-oncogene?

A

Genes that cause oncogenes to be turned on

59
Q

What condition is cuased by a mutation in the RET gene?

A

Multiple Endocrine Neoplasia Type 2 (MEN2)

60
Q

What type of cancer do people with multiple endocrine neoplasia type 2 develop?

A

a form of thyroid cancer called medullary cancer of the thyroid

61
Q

What is the nature of most loss-of-function mutations that occur in tumour suppresor genes?

A

Recessive

62
Q

What three things make cancer cells genetically unstable?

A

Unable to stop the cell cycle to allow time for repair
Unable to carry out efficient repair
Unable to undergo apoptosis

63
Q

What do DNA repair genes do?

A

Code for proteins whose normal function is to correct errors which arise when cells duplicate prior to cell division

64
Q

What factors is the rate of DNA repair dependant on?

A

Cell type, age of cell and extracellular environment

65
Q

After a cell has accumulated alot of DNA damage, what are the three states it can enter into

A

Dormancy
Apoptosis / programmed cell death
Unregulated cell division = cancer

66
Q

What can mutations in DNA repair genes lead to?

A

Failure to repair which in turn allows mutations to accumulate

67
Q

How do viruses cause DNA damage?

A

Insert their genomes into the DNA of the host cell, which can disrupt important regulatory genes

68
Q

What does the E7 protein from HPV do to promote cancer?

A

Binds to Rb to promote its degradation which allows cells to divide faster

69
Q

What are three viruses associated with cancer?

A

Papillomavirus
Hepatitis Virus
Epstein-Barr Virus

70
Q

What has lead to the discovery of many common low risk variants for different cancers in recent years?

A

Genome wide association studies

71
Q

What does the two-hit hypothesis predict?

A

That the chances for a cell with a germ-line mutation to get a second hit ie a somatic mutation is much higher than the chances of a non-carrier to get two hits in the same cell

POM GENETICS (9 decks)

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