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BIO 1A03 > T4M4- DNA mutations and applied lecture > Flashcards

T4M4- DNA mutations and applied lecture Flashcards

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1
Q

are mutations always bad?

A

no they can cause either destructive cellular responses, beneficial adaptations or be perfectly harmless

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2
Q

what can mutations be a result of

A

environmental factors, spontaneous mutations or error in DNA replication

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3
Q

what are the most common types of mutations?

A

spontaneous

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4
Q

do viruses have low or high mutation rate?

A

high

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5
Q

why are RNA viruses more prone to mutation

A

due to delicate nature of backbone
- no proofreading capability

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6
Q

what will happen to a division of cell with mutation?

A

new cell will have part of mutation

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7
Q

what happens if a mutation occurs in non dividing (post mitotic) cell in G0 phase?

A

effect of mutation is negligible

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8
Q

are mutations inherited in somatic cells?

A

no

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9
Q

are mutations inherited in germ cells? why

A

yes because germ cells produce offspring

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10
Q

what did joshua and esther lederberg’s experiment in 1952 show

A

mutations are random and not directed

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11
Q

what type of nutrients were in the experimental setup of lederberg

A

nonselective supplemented nutrients
- so that cell can grow and form bacteria

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12
Q

what was in the new selective plate?

A

antibiotic penicillin

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13
Q

what is this process of stamping called

A

replica pleating
- preserves relative arrangements of colonies relative to original plate

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14
Q

what did they find after stamping

A

only few colonies survived penicillin on plate 2

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15
Q

what did they predict about the new colonies that survived

A

carry mutation resistant to antibiotic for penicillin

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16
Q

what does the process of replica mean

A

original colony isolated from original agar and used to test

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17
Q

after testing what did they discover about the mutations?

A

it existed in population prior to exposure

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18
Q

what can repair breaks in DNA backbone?

A

DNA ligase

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19
Q

why do most cells contain DNA ligase

A

for replication and repair of single stranded breaks

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20
Q

define proofreading

A

scanning DNA for potential mismatches

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21
Q

what does a mismatch cause

A

kink in DNA molecule

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22
Q

what causes a single stranded cleavage of mismatched DNA in the backbone

A

nuclease

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23
Q

what happens once nuclease cuts the backbone

A

another enzyme removes successive nucleotides from DNA strand

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24
Q

what happens if DNA accidently incorporates uracil

A

DNA-uracil glycosylase will cleave uracil from backbone, leaving deoxyribose sugar with no base

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25
Q

what is the lack of base detected by

A

AP endonuclease

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26
Q

what does AP endonuclease do

A

cleaves backbone of lack based area, leaving gap for addition of new nucleotide

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27
Q

what happens in a base excision repair

A

damaged base is recognized and removed from the DNA backbone by one of the DNA glycosylases

28
Q

what is nucleotide excision repair similar to

A

mismatch repair

29
Q

what does a nucleotide excision repair do

A

removes and replaces one or more nucleotide bases in a “cut and patch” way

30
Q

how are bases cleaved during nucleotide excision repair

A

bases signal to enzymes to cleave DNA backbone on both sides of damaged bases

31
Q

what are small point mutations

A

single nucleotide pair changes

32
Q

where do small point mutations arise and why

A

during DNA replication due to escaping proofreading mechanisms

33
Q

what are the most common types of small point mutations

A

single nucleotide base substitution

34
Q

what is another name for single nucleotide base substitution

A

single nucleotide polymorphisms or SNP

35
Q

what mutation causes sickle cell anemia

A

a missense mutation that causes a single amino acid substitution in the hemoglobin molecule

36
Q

what happens as a result of the base change in sickle cell anemia

A

translation of valine instead of glutamate

37
Q

define missense mutation

A

when a single nucleotide base is changed, resulting in a a different amino acid

38
Q

define silent mutation

A

occurs when a change in nucleotide pair has codon substitute but still produces same amino acid
- possible due to gene redundancy

39
Q

what do most substitution mutations lead to

A

missense mutations

40
Q

what is a nonsense mutation

A

a point mutation which gives rise to an amino acid which codes for stop codon

41
Q

describe result of nonsense mutations

A

-causes premature translation termination
-has shorter polypeptide sequence
-can lead to nonfunctional proteins

42
Q

define insertion

A

when one or more extra nucleotide is inserted into replicating DNA

43
Q

define deletion

A

skipping or removing more than one nucleotide during replication

44
Q

what determines degree of impact of insertion or deletions

A

size of mutation

45
Q

what mutation causes cystic fibrosis

A

deletion of 3 nucleotides in CFTR channel

46
Q

define a frameshift mutation

A

occurs when insertion or deletion does not happen in a group of three

47
Q

what does a frameshift mutation lead to

A

-improper grouping of nucleotides
-massive missense mutations
-ends in nonsense and nonfunctional proteins

48
Q

what happens when a centromere is lost

A

entire chromosome is lost because not allocated into daughter cells

49
Q

what happens if there is a deletion in one homologous chromosome

A

organism may persist depending on if other homologue can compensate to provide gene product needed for survival

50
Q

what can chromosomal duplication cause

A

little harm due to homologous chromosome

51
Q

what can duplication lead to

A

new gene being formed with similar function to original gene

52
Q

define inversion

A

when normal sequence is reversed

53
Q

what causes an inversion?

A

a segment breaks off and reattaches in reverse order

54
Q

is inversion serious?

A

no because all genes are present

55
Q

what does inversion explain?

A

long term chromosomal evolution

56
Q

define reciprocal translocation

A

portion of one chromosome attach to non homologous chromosome and exchange terminal chromosomal fragments

57
Q

when does reciprocal translocation occur

A

happens when there is a break and translocation carried out before the break required

58
Q

where does reciprocal translocation occur

A

in non coding regions of DNA in large genome

59
Q

explain duplication and divergence effect with globin proteins in fetuses

A

two gamma globin genes are almost identical in amino acid sequence but expressed at different points

60
Q

explain duplication and divergence effect with globin proteins in adults

A

adult delta and beta hemoglobin differ in amino acid sequence and are expressed at different levels

61
Q

what are miRNAs

A

microRNAs- short non coding RNA that regulate gene expression post transcriptionally

62
Q

what are TUFs

A

transcripts of unknown function- their role in the cell is unknown

63
Q

what does the alternative splicing hypothesis state

A

eukaryotes do not require large numbers of distinct genes

64
Q

how similar are chimp and human genes?

A

98.8%

65
Q

where are the differences in genome found between chimps and humans

A

in the regulatory sequences
- responsible for phenotypic differences

BIO 1A03 (10 decks)

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