BIO226 > Topic 6 > Flashcards

Topic 6 Flashcards

(58 cards)

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1
Q

What types of mutations are passed down to offsrping?

A

mutations in germ cells

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2
Q

What is the spontaneous mutation rate in humans?

A

2-3 x 10^-8/generation aka 200-300 germline mutations/generation

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3
Q

What are the five types of DNA lesions?

A

Abasic sites
Base mismatches
Chemically modified bases
inter and intra strand crosslinks
double strnad breaks

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4
Q

What are the four types of point mutations?

A

transition-purine for purine or pyrimidine for pyrimidine
transversion- purine by pyrimidine or vice versa
deletion
insertion

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5
Q

What are synonymous mutations?

A

silent mutations

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6
Q

What are non-synonymous mutations?

A

missense
nonsense

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7
Q

What are conservative and non-conservative missense mutations

A

con-chemically similar may retain protein function
non-con-chemicially different aa-alter protein function

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8
Q

What is a nonsense mutation?

A

changes aa to a stop codon

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9
Q

What do indels increase the likelihood of?

A

premature stop codon

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10
Q

If a mutation is in regulatory regions required for gene expression what does that impact?

A

how much protein is made

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11
Q

What was the experiment that proved spontaneous mutations exist?

A

E.coli resistant to phages

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12
Q

What is slippage and when does it occur?

A

mispairing between template and synthesize strands in regions with repetitive sequences

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13
Q

What can slippage cause?

A

miss a replication of region or replicate it twice

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14
Q

What are some examples of slippage mutations?

A

Fragile X syndrome and Huntingtons disease

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15
Q

How does base mispairing primarily occur if the structures of ATCG and generally complementary of each other?

A

isomerization to tautometirc forms

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16
Q

How can DNA mispairing be corrected?

A

Klenow fragment of DNA pol or DNA repair mechanisms

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17
Q

What are the four main types of DNA damage?

A

ionization
depurination
deamination
oxidative damage

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18
Q

What causes ionization?

A

xray, gamme rays and UV

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19
Q

What causes depurination?

A

hydrolysis of sugar/base bond

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20
Q

What is depurination?

A

random loss of A or G

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21
Q

What does depurination often cause?

A

insertion

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22
Q

How can apurine sites be repaired?

A

DNA repair mechanisms

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23
Q

What is deamination?

A

loss of amine group from C, A or G by hydrolysis

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24
Q

What does deamination lead to?

Study These Flashcards
A

alters chemical affinities for base pairings leading to mutations

25
What are the main two consequences of oxidative stress?
replication stall or mismatch pairings
26
What are alkylating agents?
adding ethyl or methyl group to nucleotide
27
What does alkylation cause?
incorrect base pairings
28
What is an example of an alkylating agent and what does it do?
EMS-indices transitions in next round of DNA replication
29
What are DNA adducts?
attachment of chemicals to nitrogenated base
30
What are examples of chemicals that cause adducts?
Aflatoxin B1 and BaP
31
What comes from removing an adduct?
apurinic site
32
What are base analogs?
compounds that are chemically similar to ATCG that form associations with DNA
33
What are intercalating agents?
nitrogenated compounds that mimic base pairing and insert themselves between base pairs and DNA double strand
34
What do intercalating agents cause?
slippage of DNA pol and thus cause insertions or deletions
35
How does UV light cause DNA damage?
form pyrimidine dimers which causes DNA synthesis stalls and transition mutations
36
How does ionizing radiation cause DNA damage?
directly-DNA breaks trigger apoptosis or repairs indirectly-ROS
37
What are the 5 DNA repair systems?
Base excision repair nucleotide excision repair mismatch repair HR NHR
38
What is direct repair?
enzymes that can correct altered nucleotides after screenign
39
What are the two main DR enzymes?
photolyases-reverts pyrimidine dimers alkyltransferase-reverses bp alkylation
40
What is base excision repair?
removal and replacement of damaged bases before replication by relying on complementarity of non affected site for repairs
41
What are the three steps of BER?
a) removal of base by DNA glycolases b) polyermerization of correct base by polB c) DNA ligase
42
What does NER do?
excises large amount of bp
43
What are the steps of NER
1. damage detection 2. strand separation 3. ressection 4. excision 5. polymerization 6. ligation
44
What is an example of a disease due to a defect in NER?
Xeroderma Pigementosum
45
When does mismatch repair occur?
during DNA replication
46
What subunit recognizes the errors in MMR?
MutS
47
What does binding of MutS to the DNA cause?
recruitment of MutL and MutH
48
What does MutH do in MMR?
binds GATC sequences and nicks strand with error
49
How does MutH know which strand to cut?
it is not methylated as methylation occurs after DNA replication
50
How does the DNA get repaired in MMR?
helicase unwinds site of mismatch, exonucleases degrade nicked strands and Pol3 is recruited to resynthesize
51
Why are double stranded breaks so bad for organisms?
lose all of the repair mechanisms that rely on non broken strand
52
What are the four steps of non-homologous end joining?
1. Detection 2. Strand resection 3. polymerization 4. Ligation
53
What enzymes are involved in strand resection and what do they do?
DNA-PKcs which activates artemis to remove 5' and 3' overhanfs
54
What are the three steps of homologous end repair?
1. Detection 2. resection 3. strand exchange
55
What happens during the resection portion of HR?
3' single strand overhangs
56
What happens during strand exchange during HR?
recombinases displace sister template strands and form D loop, invading strand extended by polymerases
57
What occurs during the SDSA pathway of HR?
helicase breaks association of invading strand-orginal strands reanneal gaps, no crossing over
58
What happens during DSBR in HR?
1. second strand invades to form a holiday junction 2. resolution of intermediates to form either recombined or non recombined products
BIO226
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