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Genetics 380 > DNA Mutation and Repair > Flashcards

DNA Mutation and Repair Flashcards

(70 cards)

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1
Q

wild type sequence

A

most common (normal) seq; all changes in DNA base seq are referred to as mutations

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2
Q

mutations

A

helpful/neutral/detrimental, necessary for evolution, one mechanism whereby organisms acquire new characteristics

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3
Q

reverse mutation (reversion)

A

replaces original (forward) mutation & restores the wild type genotype and phenotype

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4
Q

suppressor muation

A

at another site but it compensates for the mutation & restore the wild type phenotype; can hide or suppress the effects of other mutations; ind is double mutant w normal phenotype

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5
Q

intragenic

A

w/i the same gene’s coding seq

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6
Q

intergenic

A

in second gene’s coding seq

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7
Q

germline mutations

A

present in either (or both) the sperm or the egg that made the ind therefore present in every cell the ind has

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8
Q

somatic mutations

A

arise after fertilization during cell replication/division/differentiation/migration therefore only present in a subset of the inds cells; arise in S phase gets passed down to 1/4th of the descendants of the original cell; occurred after fertilization and only existed in subset of parent’s cells

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9
Q

conditional mutation

A

only cause consequences under certain conditions

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10
Q

deletions & duplications

A

rand from single nucleotides to pieces of chromosome that are large enough to include many genes in them

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11
Q

inversion & translocations

A

rearrange large pieces of chromosomes

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12
Q

numerical abnormalities

A

entire chromosomes can be added or deleted

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13
Q

point mutation

A

substitution, deletion, or addition of single nucleotide

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14
Q

transition

A

purine-purine substitution or pyrimidine-pyrimidine substitution

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15
Q

transversion

A

purine-pyrimidine substitution or vise versa

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16
Q

missense mutation

A

single nucleotide substitution causes one amino acid to replace another

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17
Q

nonsense mutation

A

single nucleotide substitution creates STOP codon at site of mutation and truncates protein

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18
Q

silent muations

A

do not change organism’s phenotype

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19
Q

synonymous mutation

A

doesn’t change AA content of protein; may change splicing of mRNA

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20
Q

neutral mutation

A

changes AA content of protein but has no functional consequences

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21
Q

genetic code is degenerate

A

partially redundant

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22
Q

in-frame deletion or insertion

A

insertion/deletion involving multiple of 3 so it doesn’t shift the reading frame - AA seq will be normal before and after mutation

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23
Q

frame shift muation

A

insertion/deletion doesn’t involve multiple of 3 bases - reading frame of ribosome gets shifted; all AA after are abnormal

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24
Q

coding sequence mutation

A

change activity of each molecule of the protein

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25
mutation in promoter & other regulatory seqs
affect rate at which gene makes its protein i.e. # of protein molecules in the body
26
trinucleotide repeats
3 bases get repeated w diff people having diff # of repeated units in string; found in coding regions & regulatory sequences; can expand during meiosis; larger repeated string gets = more it disrupts gene function; expansions are most common but sometimes repeat can contract; expand vs contract depends on parent of origin - more likely to contract during spermatogenesis than oogenesis; can cause strand slippage
27
fragile X syndrome
due to expanding CGG repeat in X chromosome (Xq28) of FMR1 gene which gets methylated - silencing the gene; FraX trinucleotide repeat can also contract during meiosis - more likely during spermatogenesis, asymptomatic males carrier pass repeat to daughters who may not be affected but will pass down to children which may be big enough to affect them
28
common fragile sites
all over the genome in everyone's chromosomes - not associated w disease
29
rare fragile sites
associated w diseases ex: Fragile X syndrome - fragile site depicted here
30
genetic anticipation
when repeat expands through meiosis subsequent generations are affected earlier and more severely than previous generation
31
transposable elements (aka transposons)
move from one place to another w/i same cell's DNA; "cut and paste" and leave or make copy of themselves and "copy and paste" themselves into another location; 45% of human genome comes from transposons; generate direct flanking repeats when they insert; can disrupt genes if inserted in gene's regulatory seq but can jump back out & restore gene function
32
inverted repeats
help transposable elements break out of their places
33
transposase
enzyme that makes staggered cut in DNA; creates short single stranded overhangs that are complementary to each other; transposon inserts between ends of the cut; enables transpositions
34
inverted terminal repeat
part of transposon
35
direct flanking repeat
not part of the transposon - it is created as result of transposition process
36
retrotransposons
use reverse transcription
37
transposable element as activator
if it has seq capable of acting as promoter
38
transposable element & chromosome rearrangements
can disrupt activity of genes
39
cell methylation
methylates DNA in region of transposon which inhibits production of transposase
40
interfering RNAs
used by cell to interrupt transposase production
41
spontaneous mutations
errors during DNA replication; hydrolytic & other reactions can cause base change sin DNA after replicaiton
42
induced mutations
environmental agents such as UV light or radon; chem exposures; metabolic by products such as superoxide ion O2-
43
mutagens
agents that induce mutations
44
wobble/non Watson-Crick basepairing
ability to pair w atypical base bc of shifts in arrangement of hydrogen bonds; leads to replication errors
45
depurination
hydrolysis removes purine ring from adenine and guanines = results in mutation if not corrected quickly
46
deamination
converts between pyrimidines by hydrolysis of NH2 group
47
chemical mutagens
change # of H bonds the base makes
48
5-Bromouracil
replaces A thymine but bonds w A guanine
49
reactive oxygen species
oxidize guanine to 8-oxoguanine which pairs w/ A rather than C as G should; created by normal metabolism
50
intercalating agents
insert themselves btwn nucleotides; inc distance btwn neighboring basepairs confusing DNA polymerase & causing insertion & deletions in DNA (ex: acridine orange, ethidium bromide)
51
UV and ionizing radiation
break DNA strands; cause cells to form highly reactive free radicals = cause breaks in DNA = attempt to fix may result in mutations
52
pyrimidine dimers
caused by sun's UV rays; bonds form between neighboring Cs or Ts in same DNA strand preventing DNA rep; eukaryotes have special DNA polymerase eta that puts AA across pyrimidine dimer and restores DNA
53
mismatch repair mechanism
repairs: replication errors, including mispaired bases and strand slippage
54
direct repair mechanism
repairs: pyrimidine dimers, other specific types of alterations
55
base excision repair mechanism
repairs: abnormal bases modified bases and pyrimidine dimers
56
nucleotide excision repair mechanism
repairs: DNA damage that distorts that double helix, including abnormal bases, modified bases, and pyrimidine dimers
57
direct repair
repaired directly by chemical reactions that restore the original base w/o removing anything ex: pyrimidine dimers
58
photolyase
uses light E to break bonds in pyrimidine dimers which enables bases to make their proper bonds w their complementary bases again; direct repair
59
06-methylguanine DNA methyltransferase
removes the methyl group if guanine gets methylated; direct repair
60
base mismatches
repairs by base excision; mismatched bases forms bubbles in DNA double helix which are recognized by repair systems
61
singe nucleotide damage (ex: deaminations)
repaired by base excision
62
DNA polymerase beta
fills gap from base excision in eukaryotes; has no proofreading ability; 10 new mutations uncorrected per day: sometimes error leaves DNA ligase unable to seal gap; AP endonuclease comes in
63
AP endonuclease
returns and excises nucleotide allowing DNA polymerase beta another chance to put the right nucleotide in
64
nucleotide excision repair
1. recognize problem 2. remove bad nucleotide(s) 3. replace w proper nucleotide(s) 4. seal w DNA ligase
65
methylation
differentiates old DNA strand from new one
66
DNA damage bypass
DNA polymerase fills in 2nd gap created by excision; newly synthesized strand is available as template
67
non homologous end joining
repair double stranded breaks; ends join back together results in deletion in the chromosome
68
homology-direct repair (HDR)
repairs double stranded breaks; two types; homologous chromosome used as template to fill gap on one of the broken strands
69
non crossover synthesis dependent strand annealing (SDSA)
repairs double stranded breaks; gap in other strand is filled using newly repairs strand as template
70
double strand break repair (DSBR)
gap in other strand is filled using other strand of homologous chromosome as template

Genetics 380 (11 decks)

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