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Applied Genetics > Mutations > Flashcards

Mutations Flashcards

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
which bases are singlebing
pyrimidines
26
what is transition base pair substitution
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
27
what is transversion base pair substitution
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
what is the effect on protein sequence - nonsense mutations
change of a codon in the ORF (Open Reading Frame) to a stop codon
29
what is the effect on protein sequences - missense mutations
a base-pair change resulting in a different mRNA codon --> a different amino acid in the protein
30
what are the phenotypic effects may or may not occur
neutral mutations | silent mutations
31
what do neutral mutations cause
change of codon in open reading frame, no detectable change in function of protein
32
what do silent mutations cause
mutant codon encodes same amino acid as wild-type gene --> no change occurs in protein produced
33
what do base pair deletions or insertions cause
Change the reading frame of the mRNA downstream of the mutation, resulting in frameshift mutation
34
what happens if reading frame is shifted
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
when do frame shifts occur
result from insertions or deletions when the number of affected base pairs is not divisible by three
36
are mutations spontaneous or induced
most mutations spontaneous | some are induced
37
when can mutations occur spontaneously and what causes it
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
what is the spontaneous mutation rate in eukaryotes and in bacteria
between 10-4 and 10-6 /gene/ generation, and in bacteria and phages between 10-5 and 10-7 /gene/ generation.
39
how are spontaneous errors corrected
cellular repair systems, and so do not become fixed in DNA
40
what is the visible region of
400-700nm
41
what are induced mutations
caused by physical or chemical mutagens
42
what are the physical mutations caused by
radiation xrays (ionizing)
43
what happens when xrays penetrate tissues, what do the created ions do
knock electrons out of orbits and create ions | created ions can break covalent bonds (S-P backbone in DNA)
44
what do broken bonds in physical mutations lead to
translocations | interchanges between chromosomes
45
what does ionizing radiation do depending on doses
kills cells at high doses and lower doses produce point mutations
46
what does UV do to DNA
photochemical changes in DNA
47
what are UV wavelengths like
UV has lower-energy wavelengths than X-rays, and limited penetrating power
48
what range of UV is strongly absorbed by purines and pyrimidines what does this form
UV in the 254-260 nm forming abnormal chemical bonds
49
where do dimers form
Dimer formation between adjacent pyrimidines, commonly thymines
50
what happens if the abnormal chemical bonds caused by UV mean is enough are unpaired
Most pyrimidine dimers are repaired, as they produce a bulge in the DNA helix. If enough are unrepaired, cell death may result
51
how do chemical mutations occur what do they do depending on their action
naturally occurring or synthetic | form different groups based on their mechanism of action
52
what groups can be formed from chemical mutations
base analogues base modifying agents (alkylating agents, deaminating agents) intercalating agents
53
what are base analogues like
similar to normal nitrogen bases, and are incorporated into DNA readily
54
what happens when base analogues in DNA
shift in the analog’s form will cause incorrect base pairing during replication, leading to mutation
55
how do base modifying agents work
modifying chemical structure and properties of bases
56
what does nitrous acid do in base modifying agents
acts as a deaminating agent, converting C to U
57
what does Ethylmethanesulphonate do
alkylating agent that adds alkyl groups to bases
58
what are the advantages of using Ethylmethanesulphonate to mutate organisms
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
where are intercalating agents inserted
can be inserted between adjacent bases in dsDNA (the sugar backbone)
60
what do intercalating agents do
alter the spacing of sugar-phosphate backbone of DNA, often causing deletions and associated frameshift mutations, and they do not cause base replacement
61
how do intercalating agents affect DNA polymerase
DNA polymerase which sticks at a random nucleotides or jumps and affects its fidelity
62
what is the genetic code
genetic code - more than one codon encoding for one amino acid
63
what is the biological window in electromagnetic spectrum
300-1000nm
64
why can't DNA survive in high radiation e.g.gamma rays, xrays
energy too high | too many mutations
65
why can't DNA survive in low radiation e.g. radiowaves
not enough energy for organism to survive

Applied Genetics (20 decks)

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