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Biochem IV > Origins of Mutations > Flashcards

Origins of Mutations Flashcards

1
Q

Name three common DNA lesions

A

depurination, deamination, pyrimidine dimers

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2
Q

What is the most common deamination reaction?

A

conversion of cytosine to uracil

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3
Q

What are gene mutations?

A

variations in nucleotide sequence

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4
Q

What are chromosomal mutations?

A

changes in chromosomal regions

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5
Q

What are genomic mutations?

A

surplus or loss of chromosomes

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6
Q

Of the three, what are the most common?

A

genome mutation

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7
Q

Of the three, what are the least common?

A

gene mutation

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8
Q

What are point mutations?

A

one base exchanged for another

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9
Q

What are the three types of point mutations?

A

silent, missense, nonsense

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10
Q

When does recombination occur?

A

meiosis

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11
Q

Where are Incorrect Recombinations most likely to occur?

A

loci of genes

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12
Q

Where is strand slippage most likely to occur?

A

areas of repetitive sequence

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13
Q

What type of mutation accounts for 25% of all genetic mutations?

A

frameshift

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14
Q

What are homologous chromosomes?

A

maternal and paternal copies of the same chromosome

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15
Q

What happens in prophase of the first meiotic division?

A

the chromosomes condense and become visible by light microscopy

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16
Q

What is synapsis?

A

homologous chromosomes align

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17
Q

What is the function of the synaptonemal complex?

A

to hold the homologous chromosomes together during synapsis

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18
Q

When does crossing over occur?

A

synapsis

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19
Q

What is the function of chiasmata?

A

to hold together chromosomes after crossing over

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20
Q

What else happens at the chiasmata?

A

sites of crossovers

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21
Q

What happens to the chromosomes during metaphase?

A

positioned at the equator of the cell

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22
Q

What is disjunction?

A

during anaphase when chromosomes are separated and pulled to the poles

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23
Q

What is non-disjunction?

A

incomplete separation of chromosomes during anaphase

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24
Q

The frequency of what genetic abnormality increases with age?

A

non-disjunction

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25
Q

What term is used to describe a missing chromosome?

A

monosomy

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26
Q

Trisomy can be observed for which autosomes?

A

13, 18, 21

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27
Q

What is trisomy 13?

A

patau syndrome

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28
Q

What is trisomy 18?

A

Edward Syndrome

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29
Q

What is trisomy 21?

A

down syndrome

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30
Q

What is mosaicism?

A

When an individual is composed of both mutated and normal cells

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31
Q

Mosaicism occurs from what kind of mutations? When do these occur?

A

somatic

embryogenesis

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32
Q

How is the mutated strand of DNA recognized in DNA strand mismatch repair?

A

distortions in the DNA double helix

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33
Q

What is Lynch Syndrome?

A

hereditary non-polyposis colorectal cancer

34
Q

What causes HNPCC? What is the change of a HNPCC patient developing cancer?

A

defects in strand directed mismatch repair

80%

35
Q

What is the function of DNA glycosylases?

A

to recognize altered bases and catalyze their hydrolytic removal

36
Q

What can nucleotide excision repair do?

A

fix pyrimidine dimers

37
Q

Xeroderma pigmentosum involves mutations in protein machinery involved in what process?

A

nucleotide excision repair

38
Q

Non-homologous end joining results in what?

A

loss of a nucleotide or nucleotides at their break point

39
Q

Homologous end-joining uses what?

A

the non-damaged homologous end as a repair template

40
Q

Cytarabine is an analogue of what?

A

cytarabine is an analog of cytidine

41
Q

Cytarabine is often used in the treatment of what disease?

A

acute leukemia

42
Q

Once inside the cell, what is cytarabine triphosphate incorporated into?

A

cytarabine triphosphate

43
Q

What is cyclophosphamide often used in the treatment of?

A

Hodgkin’s Lymphoma

44
Q

What is cyclophosphamide converted into?

A

phosphoramide mustard

45
Q

What is the MOA of phosphoramide mustard?

A

forms inter and intra DNA cross-links

46
Q

What enzyme does doxorubicin inhibit?

A

topoisomerase II

47
Q

What is the MOA of doxorubicin?

A

prevents the re-ligation of double-stranded breaks

48
Q

Cytarabine is an analog of what? What does cytarabine contain?

A

cytidine

arabinose

49
Q

What is the MOA of cytarabine?

A

competes with deoxyribunucleotides for DNA polymerases

50
Q

What type of DNA mutation does strand slippage produce?

A

an insertion

51
Q

What type of DNA mutation do intercalating agents produce?

A

insertions or deletions

52
Q

What type of DNA mutation do errors in recombination produce?

A

duplicate material on one strand and delete material on the other

53
Q

Frameshift diseases account for what percentage of human genetic diseases?

A

25%

54
Q

What happens to the DNA in prophse?

A

chromosomes condense and become visible

55
Q

What is synapsis?

A

homologous chromosomes align during meiosis

56
Q

What holds the chromosomes together during synapsis?

A

synaptonemal complex

57
Q

What process takes place during synapsis?

A

crossing over

58
Q

What holds the chromatids together after the synaptonemal complex disintegrates?

A

chiasmata

59
Q

What is disjunction?

A

when chromosomes are pulled apart during anaphase

60
Q

What is nondisjunction?

A

incomplete separation of chromosomes during anaphase

61
Q

What happens during prophase?

A

chromosomes condense

62
Q

What happens during metaphase?

A

chromosomes line up on the equator

63
Q

What happens during anaphase?

A

chromosomes are pulled apart

64
Q

What does monosome mean?

A

chromosome missing

65
Q

Mosaicism occurs due to genetic defects that occur during when?

A

embryogenesis

66
Q

What DNA polymerase contains proofreading activity?

A

DNA polymerase delta

67
Q

What is the function of DNA glycosyles?

A

to recognize and remove incorrect DNA base pairs

68
Q

What does uracil DNA glycosylase do?

A

remove uracil

69
Q

What is the function of AP endonuclease?

A

cuts sugar-phosphate backbone on one side

70
Q

Pyrimidine dimers are repaired by what process?

A

nucleotide excision repair

71
Q

What type of end-joining, homologous or non-homologous, results in the loss of nucleotides?

A

non-homologous end joining

72
Q

Cyclophosphamide is used in the treatment of what disease?

A

Hodgkin’s Lymphoma

73
Q

How does cyclophosphamide inhibit cell growth?

A

inter and intra DNA alkylating agent

74
Q

What three events can lead to insertions or deletions?

A

incorrect recombination, strand slippage, intercalating

75
Q

Durign synapsis, what holds the sister chromatids close together?

A

synaptonemal complex

76
Q

After synapsis, what holds the crossed-over chromatids?

A

chiasmata

77
Q

What feature allows newly synthesized DNA to be differentiated from parental DNA?

A

newly synthesized DNA is nicked

78
Q

Where is heterochromatin concentrated?

A

periphery of nucleus

79
Q

What disease is associated in defects with nucleotide excision repair?

A

xeroderma pigmentosum

80
Q

What sugar does cytarabine contain?

A

arabinose

Biochem IV (6 decks)

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