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Genetics > Chapter 18: Gene Mutations and DNA Repair > Flashcards

Chapter 18: Gene Mutations and DNA Repair Flashcards

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Biology 101 flashcards
1
Q

Mutation

A

inheritable change in genetic information

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2
Q

Where do somatic mutations occur?

A

nonreproductive cells

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3
Q

How are somatic mutations passed?

A

through mitosis. clones of the cells are formed that have the mutant gene

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4
Q

Where do germ line mutations occur?

A

in cells that give rise to gametes via meiosis and sexual reproduction

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5
Q

What percentage of offspring will recieve the germ line mutation?

A

approximently half of the next generation

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6
Q

Base substitution

A

alters a single codon

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7
Q

What is a transition base substituition?

A

purine to purine or pyrimidine to pyrimidine

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8
Q

What is a transversion base substitution?

A

purine to pyrimidine or pyrimidine to purine

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9
Q

What gene mutation alters the reading frame and may change codons?

A

Base insertions/deletions

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10
Q

What are indels caused by?

A

strand slippage and unequal crossing over

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11
Q

What is a mutation that hides or supprots the effect of another mutation?

A

supressor mutation

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12
Q

Where must supressor mutations occur?

A

at a site that is different than the site of the original mutation

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13
Q

Where does an intragenic supressor mutation occur?

A

same gene

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14
Q

Where does an intergenic supressor mutation occur?

A

different gene

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15
Q

What type of mutation produces a new codon that encodes for a different amino acid?

A

missense mutation

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16
Q

How does a missense mutation occur?

A

via changing the amino acid sequence

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17
Q

What mutation produces a new codon that is a stop codon that prematurely terminates translation?

A

nonsense mutation

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18
Q

What type of mutation produces a new codon that encodes the same amino acid?

A

silent mutation

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19
Q

What type of mutation produces no change in amino acid sequence?

A

silent mutation

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20
Q

What factors affect mutation rates?

A

-the frequency in which change takes place
-the probability that a mutation will be detected
-the repair rate

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21
Q

What is a site that cannot provide a template for a complementary base on the newly synthesized strand?

A

apurinic site

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22
Q

When do apurinic sites occur?

A

after base modifications and DNA glycosolases come in and degrade the base via base excision repair; leaving the spot without a base and available for later repair

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23
Q

Depurination

A

loss of purine

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24
Q

Deamination

A

loss of amino group

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25
Q

Where do chemically induced mutations occur?

A

nitrogenous base

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26
Q

What induces permenant change in a nitrogenous base?

A

mutagen

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27
Q

What is a carcinogen?

A

controls mutation in cell division (cancer)

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28
Q

What can be caused by base analogs?

A

point mutations

29
Q

What is the base analog of thymine and how does it occur?

A

5-bromouracil occurs due to mispairing

30
Q

Can DNA polymerase recognize 5-bromouracil?

A

yes because it is similar to thymine (causes mutations)

31
Q

What do alkylating agents do?

A

donate alkyl group

32
Q

Deamination produces….

A

nitrous acid

33
Q

What does hydroxylamine add?

A

hydroxyl group

34
Q

Intercalating agents produce…

A

ethidium bromide

35
Q

What does radiation increase in all organisims?

A

mutation rates

36
Q

What is a pyrimidine dimer?

A

two thymine bases that block replication

37
Q

Spontaneous mutations occur when

A

DNA polymerase makes a mistake

38
Q

What are the steps that lead to mispairing?

A

-DNA strands separate for replicaton
-Thymine on the original template strand base pairs with guanine through wobble, leading to incorporated error
-Next round of replication, the G pairs with C leading to a transition mutation

39
Q

How do you detect mutations with the Ames Test?

A

-Bacterial his- strains are mixed with liver enzymes (which have the ability to convert compounds into potential mutagens) \
-Some of the bacterial strains are also mixed with the chemical to be tested for mutagenic activity
-The bacteria are then plated on medium that lacks histidine
-Bacterial colonies that appear on the plates have undergone a his- to a his+ mutation
-Any chemical that significantly increases the number of colonies on the treatment plate is mutagenic and therefore probably also carcinogenic

40
Q

What are sequences that can move about the genome?

A

transposable element

41
Q

What is transposition?

A

movement of the transposons>

42
Q

What do flanking direct repeats and terminal inverted repeats make up?

A

transposons

43
Q

How much of the genome do transposons make up?

A

~25%

44
Q

What makes staggered cuts in the DNA to create a transposon?

A

transposase

45
Q

What is transposase?

A

restriction enzyme that cuts in order for transposons to incorporate

46
Q

What is the key sign that something is a transposon?

A

replication of a single stranded DNA creates flanking repeats

47
Q

How do transposons cause mutations?

A

by inserting into another gene and promoting DNA rearrangement

48
Q

What makes up a composite transposon?

A

HAVE INSERTION SEQUENCES
-almost always has a 9-bp flanking direct repeat
-23 bp inverted repeat

49
Q

What is the transposes gene responsible for?

A

excision of transposon sequence

50
Q

What is the difference in composire and non-composite transposons?

A

there are no inverted repeat sequences in non-composite

51
Q

Where are non-composite transposons found?

A

bacteria

52
Q

How do retrotransposons work?

A

use reverse transcription to take RNA to DNA using reverse transcriptase

53
Q

What is the mechanisim of action for a transposon?

A

cut out and jump to a different part of DNA sequence

54
Q

How were transposons discovered?

A

through the studying of corn kernel phenotypes

55
Q

What is the mechanisim for mismatch repair?

A

methyhlation at the GATC sequences allows old and newly synthezised nucleotide strands to be differentiated

56
Q

What does a lag in methylation mean for mismatch repair?

A

the old strand will be methylated and the new strand will not due to the mismatched base

57
Q

How does direct repair work?

A

pyrimidine dimers can be reversed by photlyase

58
Q

What removes bases and produces apurinic sites in base excision repair?

A

DNA glycosolases

59
Q

What cleaves the phosphodiester bond in base excision repair?

A

AP endonucleases

60
Q

What end do AP endonucleases cleave on in base excision repair?

A

5’ end

61
Q

Why is Nucleotide excision repair necessary?

A

damage to the DNA, distorts the configuration of the moleucle

62
Q

What recognizes the distortion that results from the damage?

A

an enzyme complex

63
Q

What is the function of single stranded binding proteins?

A

keeps DNA from coming back together

64
Q

Homologous recombination

A

repair joins double strands while repairing mistakes

65
Q

Nonhomologuous End Joining

A

repair joins double strands while introducing insertions and deletions

66
Q

What shows that NHEJ has occured?

A

inversions

67
Q

What are the symptoms of Xeroderma Pigmentosum?

A

freclelike spots on skin, sensitivity to sunlight, predisposition to skin cancer

68
Q

What is the genetic defect that causes xeroderma pigmentosum?

A

defects in nucleotide-excision repair (specifically in the UV light repair system)

69
Q
A

Genetics (12 decks)

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