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Principles of Genetics > Mutations > Flashcards

Mutations Flashcards

1
Q

What is a mutation?

A

A change in a DNA sequence that can be heritable and is also the process of changing the DNA sequence

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2
Q

What is a mutant?

A

An organism with a mutated gene that expresses a mutant phenotype

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3
Q

What are the two things that result in genetic variation?

A

Recombination and mutation

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4
Q

What are germline mutations?

A

A mutation that is in the gametes and can be passed on to offspring

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5
Q

What are somatic mutations?

A

A mutation in somatic cells that aren’t passed to offspring, results in a genetic mosaic which results in sections with a different genetic code

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6
Q

What are point mutations?

A

Mutations that only alter one nucleotide or a short sequence

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7
Q

What are the two types of base substitutions?

A

Transition and transversion

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8
Q

What is a transition mutation?

A

A purine is changed into another purine, or a pyrimidine is changed into another pyrimidine

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9
Q

What is a transversion mutation?

A

A purine is changed into a pyrimidine, or a pyrimidine is changed into a purine

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10
Q

What are insertions and deletions? What kind of mutations can they cause? What is the effect on the protein?

A

Addition or removal of a base pair or short sequence. Can result in a frameshift mutation and a completely unfunctional protein

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11
Q

What is affected by a mutation in the promotor region?

A

RNA polymerase binding and transcription

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12
Q

What are the 4 possible results for a mutation in the promotor region?

A

Overexpression
Knockdown
Knockout/null
Silent mutation

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13
Q

What are the 3 types of mutations that can result from a base substitution in the coding region of a gene?

A

Synonymous, missense, and nonsense

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14
Q

What are synonymous mutations? What affect do they have on the protein?

A

Silent mutation. A codon is changed, but because of redundancy the new codon encodes the same amino acid. It doesn’t affect the protein

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15
Q

What are missense mutations? What is the effect on the protein?

A

A change in an amino acid. Can be conservative and be changed into a chemically similar amino acid, or non-conservative and be changed into a chemically dissimilar amino acid. Conservative missense mutations have less of an effect on the protein than non-conservative missense mutations

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16
Q

What are nonsense mutations? What is the effect on the protein?

A

A codon is change into a stop codon. Results in a truncated protein

17
Q

What 3 ways can a point mutation be described based on the effect on gene expression?

A

Silent
Knockout/null
Gain of function

18
Q

What are spontaneous mutations?

A

Random mutations that come as a result of being alive

19
Q

How often do spontaneous mutations occur?

A

Rarely at every 10^-8 nucleotides

20
Q

What are 5 mechanisms of spontaneous mutation?

A

Depurination, deamination, oxidative damage, tautomeric shifts, and replication errors

21
Q

What is depurination? What happens if it isn’t fixed?

A

A purine is missing and creates an apurinic site. When DNA is being replicated, a random base is put in the antiparallel strand to the apurinic site and can go back to normal, or can result in transition or transversion

22
Q

What is deamination? What happens if it isn’t fixed?

A

The removal of an amino group from a cytosine, which changes it into a uracil. Uracil gets paired up with adenine during replication and results in a transition mutation

23
Q

What is oxidative damage? What happens if it isn’t fixed?

A

Reactive oxygen species created normally through metabolism change guanine into 8-oxoguanine. It gets paired with adenine during replication, and results in a transversion mutation after a few rounds of replication

24
Q

What are tautomeric shifts? What happens if they don’t get fixed?

A

When a base shifts into a less common isomer called a tautomer. Normal form for T and G is keto, they shift into the enol form. Normal form for A and C is amino, they shift into the imino form. An enol T will pair with a keto G, an enol G with pair with an keto T. An imino A will pair with an amino C, an imino C will pair with an amino A. Resulted in a transition mutation

25
Q

What are replication errors? What happens if they don’t get fixed?

A

Incorrect incorporation of nucleotides and the formation of hairpins. The hairpins can lead to insertions or deletions and potentially frameshifts

26
Q

Why are repeating sequences hotspots for mutation?

A

Repeating sequences are prone to DNA polymerase slippage. They can also form hairpins with complementary base pairing

27
Q

What are induced mutations?

A

Mutations that result from the exposure to an environmental agent

28
Q

What is a mutagen?

A

An environmental agent that causes mutations

29
Q

What is mutagenesis?

A

The production of mutagens through mutagens

30
Q

What are the 4 mechanisms of induced mutations?

A

Base analogs, base alteration, intercalating agents, UV light

31
Q

What are base analogs? What happens if they don’t get fixed?

A

Bases with similar chemical structure, but don’t have the same base pairings. They are 5-bromouracil (looks like a thymine) pairs with G instead of A, 2-aminopurine (looks like an adenine) pairs with C instead of T. Results in transition mutations

32
Q

What are base alterations? What happens if they don’t get fixed?

A

Chemically altered normal nucleotides. Caused by EMS, nitrous acid, and aflatoxin. They cause transitions or transversions

33
Q

How does EMS alter the structure of nucleotides?

A

Its an alkylating agent, and adding alkyl groups results in mismatched pairings. Alkylated guanine pairs with a thymine

34
Q

How does nitrous acid alter the structure of nucleotides?

A

Deaminates bases and replaces the group with a keto group. Results in transition mutation

35
Q

How does aflatoxin alter the structure of nucleotides?

A

Attaches to guanine and causes depurination, which causes the wrong base to be put in

36
Q

What are intercalating agents? What happens if they aren’t fixed?

A

Flat molecules that look like a base pair, but get in the DNA and disrupt the double helix. They cause indels and frameshifts

37
Q

What is the effect of UV light on DNA?

A

Creates photodimers that stalls replication and results in mispairing

38
Q

What test is used to identify mutagens?

A

The Ames test

39
Q

How does the Ames test work?

A

The substance is metabolized by rat liver enzymes and then his- bacteria on minimal media are exposed to it. The reversion rate is observed. If the substance is a mutagen, lots of colonies will grow

Principles of Genetics (20 decks)

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