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Biochemistry > DNA Repair and How Mutations Occur > Flashcards

DNA Repair and How Mutations Occur Flashcards

1
Q

What happens in a deamination reaction?

A

cytosine is changed to uracil and a new amino acid will be created

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2
Q

What kind of reaction are deamination and depurination?

A

hydrolytic reactions

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3
Q

What is the most frequent of the spontaneous chemical reactions?

A

hydrolytic attack to deaminate and depurinate

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4
Q

When do these crossing over events occur?

A

in meiosis

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5
Q

Issues with dominance, recession, or codominance can be ___ disorders.

A

single gene

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6
Q

What is non-homologous end joining of DNA? What happens during its process?

A

the “quick and dirty” solution to join a double-stranded break; it deletes a few nucleotides to stitch the strands back together

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7
Q

What bonds are attacked in the hydrolytic attack of deamination and depurination?

A

C-N2H (amino group) and N-H (loss of purine ring)

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8
Q

Is there a template in non-homologous end joining of DNA?

A

NO

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9
Q

Which kind of mutation results in a single amino acid change?

A

missense mutation

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10
Q

___ facilitate and regulate the start site and process of transcription.

A

Promoters or enhancers

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11
Q

How are thymine/pyrimidine dimers removed?

A

through nucleotide excision repair

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12
Q

What delays the progression of the G1 to S phase and from S to M phases of the cell cycle?

A

non-homologous end joining and homologous recombination repairs

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13
Q

What can give rise to an allele?

A

SNPs

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14
Q

___ are sequence variants of a gene.

A

Alleles

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15
Q

What happens in a depurination reaction?

A

guanine or adenine are completely removed

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16
Q

During meiosis, the number of chromosomes ___ and the amount of DNA ___.

A

remains the same; doubles

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17
Q

Huntington’s disease is an example of an ____ mutation.

A

expanded repeat

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18
Q

What happens when a STOP codon is eliminated due to a mutation?

A

it might result in a much longer protein

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19
Q

Promoters/enhancers, splice sites, expanded repeats, and transposons are all considered ____.

A

regulatory elements

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20
Q

What is the site of crossing over referred to in homologous recombination?

A

Holliday junction

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21
Q

What unnatural base is formed from the deamination of guanine?

A

xanthine

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22
Q

What unnatural base is formed from the deamination of cytosine?

A

uracil

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23
Q

What species or component is attacked and methylated during uncontrolled methylation by S-adenosyl methionine?

A

N (nitrogen)

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24
Q

What causes induced mutations?

A

radiation or chemicals (mutagens)

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25
Q

In homologous recombination, where are the enzymes catalyzing repair found at?

A

in the nucleus

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26
Q

What happens when there is a mutation in a splice site?

A

there are nucleotides included in the mature mRNA that shouldn’t be there; results in many variations in resulting protein

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27
Q

Are somatic mutations inheritable?

A

NO

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28
Q

What results from rearrangements/translocations, deletions, insertions, and duplications?

A

chromosome disorders

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29
Q

Are most spontaneous changes in DNA temporary or permanent?

A

temporary - because they are immediately corrected by DNA repair processes

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30
Q

Where are somatic mutations located?

A

in any body cell, but not sex chromosomes

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31
Q

Where does oxidative damage to DNA occur most frequently?

A

between the CH bond on G

between the N=CH bond on A

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32
Q

What happens when 5-methyl cytosine is accidentally deaminated?

A

it turns into thymine and initiates a base change, leading to a mismatched pair on the strands

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33
Q

What is cDNA?

A

single- or double-stranded DNA sequence

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34
Q

What type of mutation results in a purine being substituted for another purine and a pyrimidine being substituted for another pyrimidine?

A

transition mutation

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35
Q

What mutation can lead to a truncated protein?

A

nonsense mutation

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36
Q

A spontaneous reaction of the deoxyribose hydrolization of N-glycosyl linkages of purine bases is called ___.

A

depurination

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37
Q

In the case of a point mutation from deamination, how many strands are affected during replication?

A

one (because the other is copied normally since the mutation did not occur on that side)

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38
Q

If each member of a chromosome pair carries a different allele, then the individual is called ___ for that gene.

A

heterozygous

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39
Q

What are the general classifications of genetic diseases?

A

chromosome disorders
single gene disorders
multifactorial or complex
sex linked and mitochondrial

40
Q

Various types of mutations in DNA can give rise to ___.

A

altered protein variants

41
Q

What guides DNA base pairing?

A

homologous recombination

42
Q

Where does uncontrolled methylation of DNA happen most frequently?

A

at the N on G and A

43
Q

What happens when the replication form encounters a nick?

A

the replication fork breaks and strand invasion must occur to restart DNA replication and reinstate the replication fork

44
Q

Cigarette smoking and lung cancer and p53 mutations are examples of ___ mutations/

A

non-inheritable

45
Q

What are the “scars” of DNA?

A

the results of non-homologous end joining (deletion of a little bit of the DNA sequence)

46
Q

How is the importance of DNA repair evident?

A

the amount of DNA enzymes present in our bodies

47
Q

The spontaneous deamination of cytosine to ___ in DNA occurs daily.

A

uracil

48
Q

What accounts for the genetic stability of our DNA?

A

accurate mechanism for replicating DNA and mechanisms for repairing DNA

49
Q

What type of mutation results in an altered protein?

A

frameshift mutation

50
Q

What might the daughter strands look like after base excision repair?

A

one is normal and one may be mutated

51
Q

____ arise naturally during DNA replication (mitosis) or during meiosis.

A

Spontaneous mutations

52
Q

____ is the exchange that takes place between a pair of homologous DNA sequences (sister chromatids).

A

Homologous recombination

53
Q

Are germline mutations inheritable?

A

YES

54
Q

Which kind of mutation causes no change in the amino acid base?

A

silent mutation

55
Q

What type of mutation occurs when a purine is substituted for a pyrimidine?

A

transversion mutation

56
Q

____ mutations occur in sex chromosomes.

A

Germline

57
Q

What type of DNA repair occurs only in the S and G2 phases?

A

homologous recombination

58
Q

___ means that genetic information gets scrambled frequently.

A

Recombination

59
Q

Where does hydrolytic attack occur most frequently on DNA?

A

at the N-C linkages to the purine ring of the deoxyribose

60
Q

Can DNA information be exchanges through the repair of a replication fork?

A

YES

61
Q

In what state will the phenotype of a recessive gene be observed?

A

homozygous

62
Q

The ___ states that genes at different loci are transmitted independently.

A

Principle of Independent Assortment

63
Q

If each member of a chromosome pair carries the same allele, then that individual is called ____ for that gene.

A

homozygous

64
Q

Which kind of mutation results in a STOP codon being produced and the protein synthesis halted?

A

nonsense mutation

65
Q

____ are mobile genetic elements that move in and out of DNA and may interfere with protein coding gene regulation or sequence.

A

Transposons

66
Q

In the nomenclature of mutations, what does “A1215T” indicate?

A

that alanine at position 1215 in the protein is changed to a threonine

67
Q

Which base cannot be deaminated?

A

thymine

68
Q

What type of mutation results in extra or missing amino acids?

A

deletion or insertion mutation

69
Q

Can mutations that occur in somatic tissues be inherited?

A

NO - but can give rise to diseases such as cancer

70
Q

In the case of a depurinated A which results in DNA deletion, how many strands will be altered during replication?

A

one (because the new strand has a deleted base and the new strand is unchanged from the T left behind)

71
Q

What is the genetic exchange between a pair of homologous DNA sequences?

A

homologous recombination

72
Q

___ alter the structure of DNA and inhibit polymerases and arrest replication.

A

Premutagenic thymine dimer

73
Q

What is used to measure the distance between two different loci?

A

a centimorgan

74
Q

The ___ states that sexually reproducing organisms possess genes that occur in pairs and that only one member of this pair is transmitted to the offspring.

A

Principle of Segregation

75
Q

What does base excision repair involve?

A

deamination and depurination reactions

76
Q

Can offspring inherit DNA breaks from radiation damage or radioactive chemicals?

A

YES

77
Q

How is DNA is test tubes renaturized or hybridized?

A

through a temperature and salt-driven process where high temperatures drives double stranded DNA into single stranded DNA

78
Q

Why is the deamination of 5-methyl cytosine not easily detected as an unnatural base when encountered by DNA repair?

A

because the deamination of it actually creates a “natural” and undetectable thymine which ends up getting incorporated into DNA without getting noticed and excised

79
Q

Is the damage to DNA repaired accurately in homologous recombination?

A

YES - damage repaired by using information from a sister chromatid

80
Q

___ are single base differences at a specific position in the genome.

A

Single nucleotide polymorphisms (SNPs)

81
Q

At what level are SNPs at?

A

the nucleotide level

82
Q

____ genes have virtually no impact on the trait.

A

Multigenic

83
Q

In what state will the phenotype of a dominant gene be observed?

A

heterozygous or homozygous

84
Q

What causes mutations?

A

spontaneous mutations and induced mutations

85
Q

What happens if there is a loss of proteins needed for DNA repair?

A

generally lead to lethal events (death to the cell)

86
Q

___ can cause the covalent linkage of two adjacent pyrimidine bases to form thymine dimers.

A

UV radiation

87
Q

What is an example of a pre-mutagenic lesion?

A

pyrimidine dimers from UV light

88
Q

What enzyme are unnatural DNA bases recognized and removed by through base excision repair?

A

DNA glycolase

89
Q

When two DNA strands switch partners between two double helices, this is called a ___.

A

Holliday junction

90
Q

The loss or alteration of what type of protein often lead to cancer in DNA replication and repair?

A

accessory proteins

91
Q

What is the mechanism to accurately repair double strand DNA breaks, exchange bits of genetic information, and assures accurate chromosome segregation during meiosis?

A

homologous recombination

92
Q

____ happens when reactive oxygen species attack the double bonds, CC, or CH bonds on DNA.

A

Oxidative damage

93
Q

What unnatural DNA base is formed from the deamination of adenine?

A

hypoxanthine

94
Q

Can pyrimidine dimers be repaired?

A

yes, by photoreactivation or nucleotide excision repair

95
Q

What type of proteins hold open DNA that cannot survive high temperatures?

A

DNA binding proteins

Biochemistry (17 decks)

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