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Biochem Exam 4 > DNA Repair and How Mutations Occur > Flashcards

DNA Repair and How Mutations Occur Flashcards

1
Q

Which type of mutation does not result in a change in the amino acid sequence?

nonsense
deletion
missense
silent

A

silent

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2
Q

What are single gene disorders?

A

caused by mutation in one particular gene

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3
Q

What are chromosome disorders?

A

broad group
-anomalies in chromosome number may not be actual mutations, just difference in numbers of genes expressed
-rearrangements
-insertions
-deletions

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4
Q

What are multifactorial or complex disorders?

A

multiple gene variants, gene variant with environment interactions
-caused by a combined effect of numerous common, low impact variants that individually would not cause disease

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5
Q

What is expressivity of a disorder ?

A

the fact that there can be different expressions in individuals that have this disorder

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6
Q

What is penetrance of a disorder?

A

the amount of people in a family that have it

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7
Q

What does variant mean?

A

gives no indication of disease state, just a different form
-still arisen by the mutation process

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8
Q

What does SNV mean?

A

single nucleotide variant

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9
Q

What are the ways to describe the frequency of a variant?

A

novel, rare, or common

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10
Q

What are the way to describe the impact of a variant?

A

low or high impact

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11
Q

What are ways to describe pathogenicity of a variant?

A

benign, likely pathogenic, or pathogenic

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12
Q

What are spontaneous mutations?

A

mutations that arise naturally during DNA replication

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13
Q

What are induced mutations?

A

caused by radiation and chemicals

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14
Q

Where can mutations occur in the DNA?

A

anywhere in the nuclear or mitochondrial DNA

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15
Q

Where are mutations located that are most heavily studied?

A

mutations that affect the protein coding sequence of genes

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16
Q

Can mutation in the introns cause disease?

A

yes

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17
Q

What are some examples of non-coding DNA?

A

gene regulatory elements, introns, and repetitive elements

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18
Q

What are silent mutations?

A

SNVs that do not change the Amino acid sequence

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19
Q

What are nonsense mutations?

A

SNVs that cause premature stop codon

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20
Q

What are missense mutation?

A

SNVs that cause a different amino acid to be brought in

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21
Q

What are conservative mutations?

A

mutations that cause an incorrect amino acid to be brought in, but have a similar side chain so there is not that big of difference seen

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22
Q

What are nonconservative mutations?

A

mutations that cause an incorrect amino acid to be brought in, but have a different sized side chain so there can be a significant difference in folding and function

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23
Q

What are deletions?

A

deletion of a single or many nucleotides in a sequence

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24
Q

What are insertions?

A

insertion of a single or many nucleotides in a sequence

25
Q

What are rearrangements?

A

When segments of DNA are moved around to place they are normally not at

26
Q

What are frameshift mutation?

A

often involve deletion of insertion of a nonfactor of 3 number of nucleotides
-causes the reading frame to be shifted

27
Q

What is an allele?

A

one of the two copies of a gene

28
Q

What is homozygous?

A

if an individual has two copies of the same allele

29
Q

What is heterozygous?

A

when an individual has one of each copies of an allele

30
Q

What does it mean if something is dominant?

A

only need one copy to have a certain phenotype

31
Q

What does it mean if something is recessive?

A

need two copies of the same allele to have that phenotype

32
Q

What causes oxidative damage to DNA?

A

reactive oxygen species

33
Q

What are the most common hydrolytic attack regions?

A

deamination and depurination

34
Q

How much depurination occurs daily?

A

around 5000 purine bases are lost each day during depurination

35
Q

How much deamination occurs daily?

A

around 100 pyrimadines lost each day during deamination

36
Q

What are some things that can cause DNA damage?

A

-reactive metabolites
-exposure to chemicals in the environment
-UV radiation (can cause thymine dimers)

37
Q

What percentage of Cytosine nucleotides are methylated in the genome?

A

around 3%

38
Q

What do methylated cytosine do?

A

help to control gene expression

39
Q

What is formed if the methyl group is removed from a cytosine?

A

thymine
*not removed by base excision repair

40
Q

What helps to remove large regions of damaged DNA?

A

nucleotide excision repair

41
Q

What removes a single nucleotide in a sequence of DNA?

A

base excision repair

42
Q

What is homologous recombination?

A

natural process that occurs during meiosis
-base pairing between DNA strands and is used to facilitate genetic exchange between homologous chromosomes

43
Q

what is non-homologous recombination?

A

does not add any base pairs to damaged DNA, just sticks the strands back together with a ligase

44
Q

Is homologous recombination associated with single stranded or double stranded breaks?

A

both

45
Q

What happens if you do not have/have mutation in repair proteins?

A

generally lethal
-or can lead to cancer

46
Q

what type of diseases are caused by the combined effect of numerous common, low impact variants that individually would not cause disease but in combination they have the potential to do so?

A

multigenic or multifactoral diseases

47
Q

what are the transitions mutations?

A

purine –> purine (A <–> G)
or
pyrimidine –> pyrimidine (C <–> T)

48
Q

what are transversions mutations?

A

purine –> pyrimidine (A/G –> C/T)
or
pyrimidine –> purine (C/T –> A/G)

49
Q

what kind of mutations causes Huntingtons and ALS?

A

repeat expression mutations

50
Q

can silent mutations cause disease?

A

yes- can cause issues with splicing region

51
Q

what type of mutation causes branchio-oto-renal (BOR) syndrome?

A

intronic variant impacting splicing

52
Q

SNP’s are generally….

A

benign

53
Q

why can cancer be difficult to treat?

A

the associated hyper-mutability

54
Q

are mutations always bad?

A

no- a very low level of mutation accumulation is important for evolution

55
Q

what is an AP site?

A

a location in DNA that has neither a purine or pyrimidine base

56
Q

what does deamination cause?

A

DNA substitution (point mutation)
*one strand remains unchanged

57
Q

what does depurination cause?

A

DNA deletion
*one strand remains unchanged

58
Q

what happens when C is deaminated?

A

changed to U

59
Q

when are mutations inherited?
in somatic tissue
in DNA of gametes

A

in DNA of gametes

Biochem Exam 4 (11 decks)

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