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Genetics Unit 4 > Lecture 1 - mutations, mutagens and dna damage repair part 1 > Flashcards

Lecture 1 - mutations, mutagens and dna damage repair part 1 Flashcards

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1
Q

Define a genotype.

A

the genetic makeup of an organism

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2
Q

Define a phenotype.

A

an organisms physical traits

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3
Q

Define wild-type.

A

the typical phenotype of an organism in nature

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4
Q

Define mutation.

A

a heritable change in the genetic material of an organism (DNA or RNA)

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5
Q

What is a NEUTRAL mutation?

A

it does not affect survival or reproductive success

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6
Q

What is DELETERIOUS mutation?

A

this decreases the chances of survival or reproductive success

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7
Q

What is BENEFICIAL mutation?

A

it increases the chances of survival or reproductive success

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8
Q

What is LETHAL mutation?

A

death as a phenotype… (recall conditional lethal (temperature sensitive))

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9
Q

What is a mutant?

A

an individual, organism, or new genetic character arising or resulting from a mutation

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10
Q

What happens during a transition mutation?

A

this is when a purine (A,G) changes to another different purine or a pyrimidine (C, T) changes to another pyrimidine

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11
Q

What happens during a transversion mutation?

A

a purine changes to a pyrimidine or a pyrimidine changes to a purine

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12
Q

What are the two ways of classifying a mutation by how it changes its DNA sequence?

A

transition and transversion mutation

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13
Q

What are the ways of classifying a mutation by how it changes its protein sequence?

A

missense, nonsense and silent mutations

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14
Q

What occurs during a missense mutation?

A

it changes a codon so that it codes for a different amino acid

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15
Q

What happens during a nonsense mutation?

A

it changes a codon that codes for an amino acid to a STOP codon

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16
Q

What happens during a silent mutation?

A

it changes a codon to a different codon that codes for the SAME amino acid… The sequence of DNA changes but the sequence of protein does not change

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17
Q

What is a point mutation?

A

a change in a single base pair

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18
Q

What is a point mutation also known as? Why?

A

a missense mutation because the point mutation changed the protein sequence (missense mutation)

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19
Q

What occurs during an insertion mutation?

A

one or more nucleotides are added to the DNA sequence

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20
Q

What occurs during a deletion mutation?

A

one or more nucleotides are removed from a DNA sequence

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21
Q

Describe a frameshift mutation.

A

the insertion or deletion of a number of nucleotides that is not divisible by 3. The frameshift mutations change the reading frame of the sequence.

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22
Q

What is a forward mutation?

A

a mutation that changes a functional (wild-type) gene to a mutant gene

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23
Q

What is a reverse mutation?

A

any mutation that restores the wild-type phenotype to cells that have a forward mutation

24
Q

What is true reversion?

A

a reverse mutation that restores the wild-type DNA sequence

25
Q

What is suppression?

A

a mutation at a second (different) site that compensates for the first mutation

26
Q

What is an intragenic suppression?

A

when the suppressor mutation occurs in the same gene

27
Q

What does intergenic mean?

A

when the suppressor mutation occurs in a different gene

28
Q

What do intragenic suppressor mutations do?

A

they revert the phenotypic effects of another mutation in the same protein

29
Q

What does the wild-type protein contain that makes an electrostatic interaction?

A

glutamic acid and arginine residues

30
Q

What does a forward mutation do?

A

it changes the arginine (positive charge) to aspartic acid (negative charge)

31
Q

What does the second intragenic suppressor mutation change?

A

the glutamic acid (negative charge) changes to lysine (positive charge) which restores the electrostatic interaction so the protein folds properly… therefore this is an intragenic suppressor mutation

32
Q

What do intergenic suppressor mutations revert?

A

the phenotypic effects of another mutation in a different protein

33
Q

A mutation that inactivates one protein can be compensated for by what?

A

a mutation that in a transcription factor that activates expression of a second gene that can compensate for the inactivated protein

34
Q

What is nonsense suppression?

A

this reverts a nonsense mutation through a second site mutation

35
Q

What does truncated mean?

A

to be cut short

36
Q

Define a spontaneous mutation.

A

a change in DNA structure that results from natural biological or chemical processes

37
Q

Define an induced mutation.

A

a change in DNA structure that is caused by an environmental agent

38
Q

What is depurination?

A

the linkage between a purine ( A or G) and deoxyribose can spontaneously break. If not repaired this can lead to mutation

39
Q

When does depurination occur?

A

it occurs when a purine base is removed from the DNA leaving an apurinic site

40
Q

What does the apurinic site NOT have?

A

it does not have a base for DNA polymerase to use as a template during replication

41
Q

Since any of the four bases can be added across the apurinic site, what may occur?

A

mutations

41
Q

What is deamination?

A

when cytosine or 5-methylcytosine can spontaneously deaminate to create uracil or thymine

42
Q

The deamination of Cytosine produces what?

A

Uracil
*dna repair enzymes can recognize U bases in DNA and correct this

43
Q

The deamination of 5-methyl-C produces what?

A

Thymine (T)
* T is a natural DNA base, so there is no system to correct this

44
Q

What is a tautomer?

A

structural isomers of a chemical compound that can readily interconvert

45
Q

What tautomer’s can G and T interconvert into?

A

the keto (common) and enol (rare) tautomer’s

46
Q

What tautomer’s can A and C interconvert into?

A

the amino (common) and imino (rare) tautomer’s

47
Q

What does tautomerization change?

A

base pairing

48
Q

What are reactive oxygen species?

A

products of oxygen metabolism in aerobic organisms

49
Q

What are some examples of reactive oxygen species?

A

hydrogen peroxide, superoxide and hydroxyl radicals

50
Q

What does superoxide dismutase do?

A

it breaks down superoxide into molecular oxygen and hydrogen peroxide

50
Q

What does catalase do?

A

it breaks down hydrogen peroxide into water and oxygen

51
Q

What does oxidative damage convert G into?

A

8-oxoG

52
Q

What is a trinucleotide repeat expansion?

A

a three nucleotide repeat can increase in number from one generation to the next

53
Q

What is a key property of trinucleotide repeat expansion?

A

DNA hairpin formation

54
Q

DNA hairpin formation can cause DNA polymerase to what?

A

to be releases from the DNA

55
Q

If DNA synthesis resumes while the hairpin is still present, what happens?

A

this will extend the repeat

Genetics Unit 4 (4 decks)

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