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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
What term is used to describe a missing chromosome?
monosomy
26
Trisomy can be observed for which autosomes?
13, 18, 21
27
What is trisomy 13?
patau syndrome
28
What is trisomy 18?
Edward Syndrome
29
What is trisomy 21?
down syndrome
30
What is mosaicism?
When an individual is composed of both mutated and normal cells
31
Mosaicism occurs from what kind of mutations? When do these occur?
somatic embryogenesis
32
How is the mutated strand of DNA recognized in DNA strand mismatch repair?
distortions in the DNA double helix
33
What is Lynch Syndrome?
hereditary non-polyposis colorectal cancer
34
What causes HNPCC? What is the change of a HNPCC patient developing cancer?
defects in strand directed mismatch repair 80%
35
What is the function of DNA glycosylases?
to recognize altered bases and catalyze their hydrolytic removal
36
What can nucleotide excision repair do?
fix pyrimidine dimers
37
Xeroderma pigmentosum involves mutations in protein machinery involved in what process?
nucleotide excision repair
38
Non-homologous end joining results in what?
loss of a nucleotide or nucleotides at their break point
39
Homologous end-joining uses what?
the non-damaged homologous end as a repair template
40
Cytarabine is an analogue of what?
cytarabine is an analog of cytidine
41
Cytarabine is often used in the treatment of what disease?
acute leukemia
42
Once inside the cell, what is cytarabine triphosphate incorporated into?
cytarabine triphosphate
43
What is cyclophosphamide often used in the treatment of?
Hodgkin's Lymphoma
44
What is cyclophosphamide converted into?
phosphoramide mustard
45
What is the MOA of phosphoramide mustard?
forms inter and intra DNA cross-links
46
What enzyme does doxorubicin inhibit?
topoisomerase II
47
What is the MOA of doxorubicin?
prevents the re-ligation of double-stranded breaks
48
Cytarabine is an analog of what? What does cytarabine contain?
cytidine arabinose
49
What is the MOA of cytarabine?
competes with deoxyribunucleotides for DNA polymerases
50
What type of DNA mutation does strand slippage produce?
an insertion
51
What type of DNA mutation do intercalating agents produce?
insertions or deletions
52
What type of DNA mutation do errors in recombination produce?
duplicate material on one strand and delete material on the other
53
Frameshift diseases account for what percentage of human genetic diseases?
25%
54
What happens to the DNA in prophse?
chromosomes condense and become visible
55
What is synapsis?
homologous chromosomes align during meiosis
56
What holds the chromosomes together during synapsis?
synaptonemal complex
57
What process takes place during synapsis?
crossing over
58
What holds the chromatids together after the synaptonemal complex disintegrates?
chiasmata
59
What is disjunction?
when chromosomes are pulled apart during anaphase
60
What is nondisjunction?
incomplete separation of chromosomes during anaphase
61
What happens during prophase?
chromosomes condense
62
What happens during metaphase?
chromosomes line up on the equator
63
What happens during anaphase?
chromosomes are pulled apart
64
What does monosome mean?
chromosome missing
65
Mosaicism occurs due to genetic defects that occur during when?
embryogenesis
66
What DNA polymerase contains proofreading activity?
DNA polymerase delta
67
What is the function of DNA glycosyles?
to recognize and remove incorrect DNA base pairs
68
What does uracil DNA glycosylase do?
remove uracil
69
What is the function of AP endonuclease?
cuts sugar-phosphate backbone on one side
70
Pyrimidine dimers are repaired by what process?
nucleotide excision repair
71
What type of end-joining, homologous or non-homologous, results in the loss of nucleotides?
non-homologous end joining
72
Cyclophosphamide is used in the treatment of what disease?
Hodgkin's Lymphoma
73
How does cyclophosphamide inhibit cell growth?
inter and intra DNA alkylating agent
74
What three events can lead to insertions or deletions?
incorrect recombination, strand slippage, intercalating
75
Durign synapsis, what holds the sister chromatids close together?
synaptonemal complex
76
After synapsis, what holds the crossed-over chromatids?
chiasmata
77
What feature allows newly synthesized DNA to be differentiated from parental DNA?
newly synthesized DNA is nicked
78
Where is heterochromatin concentrated?
periphery of nucleus
79
What disease is associated in defects with nucleotide excision repair?
xeroderma pigmentosum
80
What sugar does cytarabine contain?
arabinose

Biochem IV (6 decks)

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