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Applied Genetics > Mutations > Flashcards

Mutations Flashcards

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1
Q

what are bases

A

one of the molecular components of DNA

there are 5 types: Adenine, Guanine, Cytosine and Thymine (in DNA) or Uracil (in RNA)

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2
Q

what is a nucleoside

A

a component of nucleic acid consisting of a base linked to either a ribose or a deoxyribose molecule

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3
Q

what is a nucleotide

A

made of a base, a sugar and a phosphate group

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4
Q

what is a codon

A

a triplet of bases in the RNA to encode for an amino acid or a punctuation point in the synthesis of protein

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5
Q

what are mutations

A

any change in genetic information relative to a reference “wild-type” genome

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6
Q

what is a mutagen

A

any agent causing mutations

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7
Q

what is DNA polymerase

A

an enzyme catalyzing synthesis or breakdown of DNA

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8
Q

what is the mutation rate

A

probability of a particular kind of mutation as a function of time

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9
Q

what is the mutation frequency

A

number of occurrences of a particular kind of mutation

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10
Q

what are the types of mutations

A

point mutations
small insertions, deletions
gene duplications
major chromosomal change

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11
Q

examples of mutation sources

A

DNA polymerase errors during DNA replication
external effects - chemicals, radiation
failure of repair mechanisms

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12
Q

what is the importance of mutations

A

genes carry information needed for all of RNA and proteins in organism
survival and stability of each species depend on faithful replication of genetic information by each new generation

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13
Q

are mutations desired

A

low level of mutational change is highly desirable to provide the ability for species to adapt to changing environments

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14
Q

what mechanisms induce mutations

A 
physical mutations 
- xrays
- UV light
chemical mutagens
- base analogues 
- base modifying agents (alkylating agents, deaminating agents)
- intercalating agents
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15
Q

where do somatic mutation

A

occurs in somatic cells

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16
Q

what does somatic mutation affect

A

only individual mutation occurs in

not inherited

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17
Q

where do germ line mutations occur

A

the germ-line of sexually reproducing organisms

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18
Q

how are germ line mutations caused

A

May be transmitted by gametes to the next generation

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19
Q

what does a germ line mutation cause

A

Produces an individual with mutations in both somatic and germ-line cell

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20
Q

what are point mutations

A

involve only one base pair

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21
Q

what are the two point mutations

A
  1. Base-pair substitutions

2. Base-pair deletions or insertions

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22
Q

which bases are double ring

A

purine

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23
Q

which bases are purine

A

A G

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24
Q

which bases are pyrimidines

A

C U T

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25
Q

which bases are singlebing

A

pyrimidines

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26
Q

what is transition base pair substitution

A

replacement of a base of the same chemical category (Purine by purine AG or pyrimidine by pyrimidine CT). Represented as: G∙C –> A∙T in double stranded DNA

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27
Q

what is transversion base pair substitution

A

replacement of a base of one chemical category by a base of the other (Purine by pyrimidine ~A –> C, A –> T,G –> C,G –> T or pyrimidine by purine CA, C –>G, T –> A, T –> G) Represented as: G∙C –> T∙A in the double stranded DNA

28
Q

what is the effect on protein sequence - nonsense mutations

A

change of a codon in the ORF (Open Reading Frame) to a stop codon

29
Q

what is the effect on protein sequences - missense mutations

A

a base-pair change resulting in a different mRNA codon –> a different amino acid in the protein

30
Q

what are the phenotypic effects may or may not occur

A

neutral mutations

silent mutations

31
Q

what do neutral mutations cause

A

change of codon in open reading frame, no detectable change in function of protein

32
Q

what do silent mutations cause

A

mutant codon encodes same amino acid as wild-type gene –> no change occurs in protein produced

33
Q

what do base pair deletions or insertions cause

A

Change the reading frame of the mRNA downstream of the mutation, resulting in frameshift mutation

34
Q

what happens if reading frame is shifted

A

incorrect amino acids are usually incorporated
frameshift may bring stop codons into the reading frame, creating a shortened protein
may result in read-through of stop codons, resulting in a longer protein

35
Q

when do frame shifts occur

A

result from insertions or deletions when the number of affected base pairs is not divisible by three

36
Q

are mutations spontaneous or induced

A

most mutations spontaneous

some are induced

37
Q

when can mutations occur spontaneously and what causes it

A

All types of point mutations can occur spontaneously, during S, G1 and G2 phases of the cell cycle, or by the movement of transposons

38
Q

what is the spontaneous mutation rate in eukaryotes and in bacteria

A

between 10-4 and 10-6 /gene/ generation, and in bacteria and phages between 10-5 and 10-7 /gene/ generation.

39
Q

how are spontaneous errors corrected

A

cellular repair systems, and so do not become fixed in DNA

40
Q

what is the visible region of

A

400-700nm

41
Q

what are induced mutations

A

caused by physical or chemical mutagens

42
Q

what are the physical mutations caused by

A

radiation xrays (ionizing)

43
Q

what happens when xrays penetrate tissues, what do the created ions do

A

knock electrons out of orbits and create ions

created ions can break covalent bonds (S-P backbone in DNA)

44
Q

what do broken bonds in physical mutations lead to

A

translocations

interchanges between chromosomes

45
Q

what does ionizing radiation do depending on doses

A

kills cells at high doses and lower doses produce point mutations

46
Q

what does UV do to DNA

A

photochemical changes in DNA

47
Q

what are UV wavelengths like

A

UV has lower-energy wavelengths than X-rays, and limited penetrating power

48
Q

what range of UV is strongly absorbed by purines and pyrimidines what does this form

A

UV in the 254-260 nm forming abnormal chemical bonds

49
Q

where do dimers form

A

Dimer formation between adjacent pyrimidines, commonly thymines

50
Q

what happens if the abnormal chemical bonds caused by UV mean is enough are unpaired

A

Most pyrimidine dimers are repaired, as they produce a bulge in the DNA helix. If enough are unrepaired, cell death may result

51
Q

how do chemical mutations occur what do they do depending on their action

A

naturally occurring or synthetic

form different groups based on their mechanism of action

52
Q

what groups can be formed from chemical mutations

A

base analogues
base modifying agents (alkylating agents, deaminating agents)
intercalating agents

53
Q

what are base analogues like

A

similar to normal nitrogen bases, and are incorporated into DNA readily

54
Q

what happens when base analogues in DNA

A

shift in the analog’s form will cause incorrect base pairing during replication, leading to mutation

55
Q

how do base modifying agents work

A

modifying chemical structure and properties of bases

56
Q

what does nitrous acid do in base modifying agents

A

acts as a deaminating agent, converting C to U

57
Q

what does Ethylmethanesulphonate do

A

alkylating agent that adds alkyl groups to bases

58
Q

what are the advantages of using Ethylmethanesulphonate to mutate organisms

A

not volatile (so it is less likely to be breathed in)
soluble in water (this solution then becomes very mutagenic
Can be left over night and it becomes completely inactive; so it can be disposed of safely

59
Q

where are intercalating agents inserted

A

can be inserted between adjacent bases in dsDNA (the sugar backbone)

60
Q

what do intercalating agents do

A

alter the spacing of sugar-phosphate backbone of DNA, often causing deletions and associated frameshift mutations, and they do not cause base replacement

61
Q

how do intercalating agents affect DNA polymerase

A

DNA polymerase which sticks at a random nucleotides or jumps and affects its fidelity

62
Q

what is the genetic code

A

genetic code - more than one codon encoding for one amino acid

63
Q

what is the biological window in electromagnetic spectrum

A

300-1000nm

64
Q

why can’t DNA survive in high radiation e.g.gamma rays, xrays

A

energy too high

too many mutations

65
Q

why can’t DNA survive in low radiation e.g. radiowaves

A

not enough energy for organism to survive

Applied Genetics (20 decks)

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