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Biology Of Cancer > Lecture 7 > Flashcards

Lecture 7 Flashcards

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0
Q

Where do somatic mutations occur? Are they heritable?

A

Non-germline tissues; non-heritable

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1
Q

What are the three types of mutations?

A

Single base substitution, insertion, deletion

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2
Q

Where do germline mutations occur? Are they heritable?

A

Egg or sperm; are heritable

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3
Q

What mutation causes cancer family syndrome?

A

Germline mutations

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4
Q

Do most cancers arise from somatic or germline mutations?

A

Somatic

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5
Q

Are acquired mutations found in some or all cells of the body?

A

Some

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6
Q

What are some internal factors that can damage DNA?

A

Depurination, deamination, reactive oxygen species

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7
Q

When and where does depurination occur?

A

Spontaneously; in aqueous solution

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8
Q

What does depurination result in?

A

An abasic site (loss of nucleotide base)

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9
Q

When and where does deamination occur?

A

Spontaneously and under neutral pH

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10
Q

What does deamination result in?

A

Changes in DNA sequence (mutation), unless repaired

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11
Q

How do reactive oxygen species damage DNA?

A

Oxidation of nucleotide bases

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12
Q

What three enzymes eliminate reactive oxygen species?

A

Superoxide dismutase, glutathione peroxidase, and catalase

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13
Q

What reaction does superoxide dismutase catalyze?

A

Superoxide (O2-) –> hydrogen peroxide (H2O2)

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14
Q

What reaction does glutathione peroxidase + catalase catalyze?

A

Hydrogen peroxide (H2O2) –> hydroxyl radical (OH-) –> water

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15
Q

What is carcinogenesis?

A

Process by which normal cells are transformed into cancer cells

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16
Q

What kind of DNA damage does UV radiation cause?

A

Covalent cross links between adjacent thymines –> thymine dimers

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17
Q

What was the first discovered chemical carcinogen?

A

Benzo[a]pyrene (BP)

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18
Q

Where is benzo[a]pyrene found, and what does it cause?

A

Found in chimney soot, tar, tobacco smoke, combustion products; causes Chimney sweep’s cancer

19
Q

What is the structure of benzo[a]pyrene?

A

Polycyclic aromatic hydrocarbon (PAH)

20
Q

What are the three major categories of carcinogens?

A

Alkylating agents, aralkylating agents, and arylhydroxyamines

21
Q

What do the three major classes of carcinogens have in common?

A

Compose 95% of all carcinogens, are electrophiles which will react with amines or double bonded oxygens, and they can covalently bind DNA

22
Q

What is a DNA adduct?

A

Piece of DNA covalently bonded to a carcinogen

23
Q

What are direct carcinogens?

A

Carcinogens that can readily and directly bind DNA

24
Q

What are indirect carcinogens?

A

Compounds that are not carcinogenic themselves, but can be turned into one in the body

25
Q

What are two examples of indirect carcinogens?

A

Benzopyrene and aflatoxin

26
Q

What is biotransformation?

A

Process by which the body modifies chemical toxins to make them more water soluble and thus increase the rate of its secretion

27
Q

Which enzymes are primarily responsible for biotransformation?

A

Cytochrome P450 enzymes

28
Q

Alkylation of DNA forms what structure?

A

A DNA adduct

29
Q

What is the Ames test?

A

Test using bacteria to screen for carcinogens that cause mutation

30
Q

How does tissue organization help prevent mutations?

A

Stem cells are located to the interior of the organ

31
Q

Proofreading of the genome is accomplished by what activity?

A

3’-5’ exonuclease activity

32
Q

What two steps ensure replicative fidelity of the genome?

A
  1. Selection of the correct nucleotide to be incorporated 2. Proofreading activity of polymerase
33
Q

What are melanosomes?

A

Granules (vesicles) containing melanin

34
Q

What does melanin protect against?

A

UV radiation

35
Q

What is the function of the glutathione S-transferase (GST) family of enzymes?

A

Catalyze the conjugation of glutathione to chemical compounds to help in detoxification

36
Q

What is glutathione a tripeptide of?

A

Glutamic acid, cysteine, and glycine

37
Q

What gives glutathione its detox ability?

A

Sulfhydryl group of cysteine

38
Q

What are the 3 phases of biotransformation?

A
  1. Modification 2. Conjugation 3. Excretion
39
Q

What enzymes are responsible for biotransformation modification?

A

Cytochrome P450 class enzymes

40
Q

What enzymes are responsible biotransformation conjugation?

A

Glutathione S-transferase

41
Q

How can cells circumvent senescence (in culture)?

A

Expression of SV40 large T (LT) antigen

42
Q

What effect does SV40 LT antigen have in the cell?

A

Sequesters and inactivated tumor suppressor proteins pRB and p53

43
Q

Mutations in this gene can cause abnormal senescence

A

BRCA1

44
Q

Is inducing senescence alone enough to treat cancer cells?

A

No, cancer cells can circumvent senescence

Biology Of Cancer (14 decks)

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