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SL12003 Genetics > Mutation > Flashcards

Mutation Flashcards

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Biology 101 flashcards
1
Q

polymorphism

A

any genetic difference among individuals that is present in multiple individuals in a population

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2
Q

somatic mutation

A

occur in nonreproductive cells
passed via mitosis

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3
Q

germ-line mutations

A

occur in cells that give rise to gametes
meiosis transmission
heritable
raw material for evolution

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4
Q

sequential somatic mutations in cancer

A

series of mutations occur in the descendants of a single somatic cell. The first mutation occurs in a gene called APC, which normally inhibits abnormal cellular growth. The mutant APC cells begin to proliferate, but slowly.
Because mutations occur randomly and independently of existing mutations, there is a chance that one of the descendant APC cells will undergo a mutation in a gene called Ras. When a Ras mutation happens in a cell already carrying APC, the mutant cells divide even faster than before, but are still not malignant. But as they proliferate, there is a chance that one of the descendant cells will undergo a mutation in the gene p53.
This third mutation allow cells with further DNA damage to survive and divide extremely rapidly. And the cell lineage becomes malignant colon cancer

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5
Q

genetic risk factor

A

mutation that increases the risk of disease in an individual

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6
Q

multiple-mutation model for cancer development

A

Most human cancers require more than the overactivation of one oncogene or the inactivation of a single tumour suppressor

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7
Q

mutation rates

A

number of new mutations per genome per generation is not especially variable
mutation rate per genome per replication constant
higher for species with smaller genomes
greater rate of mutation in somatic cells

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8
Q

male mutation bias

A

mutation rate is higher in the male germline (sperm cells) compared to the female germline (egg cells). spermatogenesis throughout life time
most new mutations originate in males
older fathers-mutation rate increasing

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9
Q

indels

A

cant tell which sequence had an insertion/deletion

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10
Q

wobble base pairing

A

occurs with point mutations (substitutions)

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11
Q

transition

A

substitution of a purine for a purine or of a pyrimidine for a pyrimidine
small change in structural difference

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12
Q

pyrimidines

A

thymine and cytosine

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13
Q

purines

A

adenine and guanine

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14
Q

transversions

A

substitution of a pyrimidine for a purine or vice versa

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15
Q

transition:transversion

A

transitions more common
2:1
rate

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16
Q

copy number variation

A

form of genetic variation
number of copies of a particular segment of DNA varies between individual.
duplicated/deleted regions that include one or more genes
CNVs in coding regions cause tandem copies

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17
Q

tandem repeats

A

type of CNV
repeated sequences of DNA where the number of copies vary among individuals
the number of copies variation generates different alleles
DNA fingerprinting

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18
Q

how X rays cause mutation

A

cause breaks in the sugar-phosphate backbone

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19
Q

how UV light causes mutation

A

causes adjacent pyrimidines to cross -link forming thymine dimers which blocks replication

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20
Q

highly reactive chemicals and mutation

A

tend to be mutagenic as they can add bulky side groups to the bases
hinders proper base pairing

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21
Q

bleach/hydrogen peroxide and mutation

A

can cause loss of a base
gaps

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22
Q

tobacco smoke and mutation

A

adds bulky side groups to bases
improper base pairing

23
Q

pyrimidine dimer

A

two thymine bases
block replication

24
Q

SOS system bacteria

A

by pass replication block with a mutation-prone pathway

25
Q

strand slippage, insertions

A

newly synthesised strand loops out resulting in the addition of a nucleotide on the new strand

26
Q

strand slippage, deletions

A

template strand loops out resulting in the omission of one nucleotide on the new strand

27
Q

repeated sequences have a —–rate of strand slippage

A

higher

28
Q

unequal crossing over

A

if homologous chromosomes misalign during crossing over, one cross over product contains an insertion and the other a deletion
also caused by repeated sequences

29
Q

repeat expansions

A

type of insertion
increase in number of copies of group of nucleotides beyond normal range
can be caused by repetitive sequences

30
Q

fragile-X chromosome

A

constriction on long arm
CGG repeat expansion
strand slippage causes some individuals to have too many copes of it
more common in males

31
Q

repeat expansion mechanism

A

DNA molecule normally has x copies of a repeat (eg CAG)
the 2 strands separate and replicate and in the course of replication, a hairpin forms on the newly synthesised strand (strand slippage)
part of template strand is replicated twice; increasing number of repeats on the newly synthesised strand
the newly synthesised strand acts as template next round so the resulting DNA molecule has >x copies of the (CAG) repeat

32
Q

transposable elements/transposons

A

DNA sequences that can move from one position to another in the genome
can insert into a gene and disrupt its function

33
Q

types of DNA damage repair

A

post-replication mismatch repair
base excision repair
nucleotide excision repair

34
Q

DNA ligase

A

seals breaks in the sugar-phosphate backbone
uses energy from ATP to join the 3’ OH to 5’ phosphate

35
Q

post-replication mismatch repair

A

a single mispaired base is repaired by removing and replacing a DNA segment.

36
Q

base excision repair

A

the incorrect base and its sugar are excised from the strand then replaced

37
Q

nucleotide excision repair

A

recognises multiple mismatched bases in a region

38
Q

mismatch repair mechanism

A

mismatched bases recognised and a repair enzyme breaks the backbone downstream. another enzyme removes successive nucleotides, including the mismatched one. DNA polymerase adds the missing bases, DNA ligase joins backbones

39
Q

base excision repair mechanism

A

enzyme recognises incorrect base and binds with the site, cleaving the base from the deoxyribose sugar. a different enzyme AP endonuclease recognises the site with missing base and binds with DNA to cleave the backbone in 2 places to free the sugar. leaves a gap. other enzymes bind with the site of the gap and insert a nucleotide with proper base pairing

40
Q

nucleotide excision repair mechanism

A

one or more damaged bases signal repair process, enzymes cleave DNA backbone at these sites. region with damaged bases removed, gap filled by new DNA synthesis

41
Q

forward mutation

A

wild type to mutant type

42
Q

reverse mutation

A

mutant type to wild type

43
Q

silent mutation

A

doesnt change amino acid sequence
codon to synonymous codon

44
Q

missense mutation

A

amino acid to different amino acid

45
Q

nonsense mutation

A

sense codon to nonsense (stop) codon
(introduction of premature stop codon)
causes truncation where nearly all truncated proteins are nonfunctional and unstable

46
Q

deleterious mutations

A

decrease fitness
most extreme are lethal mutations

47
Q

advantageous mutations

A

increase fitness

48
Q

neutral mutations

A

no effect on fitness

49
Q

epistasis

A

mutations effect in fitness also dependent on genetic background (other genes)

50
Q

loss-of-function mutations

A

common
normally recessive

51
Q

gain of function mutations

A

uncommon
normally dominant

52
Q

conditional mutation

A

effect of mutation depends on something else, eg environmental condition

53
Q

suppressor mutations

A

a mutation that hides or suppresses effects of another
can be inter or intragenic

54
Q
A

SL12003 Genetics (11 decks)

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