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Biochemistry > DNA Repair and How Mutations Occur > Flashcards

DNA Repair and How Mutations Occur Flashcards

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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
In homologous recombination, where are the enzymes catalyzing repair found at?
in the nucleus
26
What happens when there is a mutation in a splice site?
there are nucleotides included in the mature mRNA that shouldn't be there; results in many variations in resulting protein
27
Are somatic mutations inheritable?
NO
28
What results from rearrangements/translocations, deletions, insertions, and duplications?
chromosome disorders
29
Are most spontaneous changes in DNA temporary or permanent?
temporary - because they are immediately corrected by DNA repair processes
30
Where are somatic mutations located?
in any body cell, but not sex chromosomes
31
Where does oxidative damage to DNA occur most frequently?
between the CH bond on G | between the N=CH bond on A
32
What happens when 5-methyl cytosine is accidentally deaminated?
it turns into thymine and initiates a base change, leading to a mismatched pair on the strands
33
What is cDNA?
single- or double-stranded DNA sequence
34
What type of mutation results in a purine being substituted for another purine and a pyrimidine being substituted for another pyrimidine?
transition mutation
35
What mutation can lead to a truncated protein?
nonsense mutation
36
A spontaneous reaction of the deoxyribose hydrolization of N-glycosyl linkages of purine bases is called ___.
depurination
37
In the case of a point mutation from deamination, how many strands are affected during replication?
one (because the other is copied normally since the mutation did not occur on that side)
38
If each member of a chromosome pair carries a different allele, then the individual is called ___ for that gene.
heterozygous
39
What are the general classifications of genetic diseases?
chromosome disorders single gene disorders multifactorial or complex sex linked and mitochondrial
40
Various types of mutations in DNA can give rise to ___.
altered protein variants
41
What guides DNA base pairing?
homologous recombination
42
Where does uncontrolled methylation of DNA happen most frequently?
at the N on G and A
43
What happens when the replication form encounters a nick?
the replication fork breaks and strand invasion must occur to restart DNA replication and reinstate the replication fork
44
Cigarette smoking and lung cancer and p53 mutations are examples of ___ mutations/
non-inheritable
45
What are the "scars" of DNA?
the results of non-homologous end joining (deletion of a little bit of the DNA sequence)
46
How is the importance of DNA repair evident?
the amount of DNA enzymes present in our bodies
47
The spontaneous deamination of cytosine to ___ in DNA occurs daily.
uracil
48
What accounts for the genetic stability of our DNA?
accurate mechanism for replicating DNA and mechanisms for repairing DNA
49
What type of mutation results in an altered protein?
frameshift mutation
50
What might the daughter strands look like after base excision repair?
one is normal and one may be mutated
51
____ arise naturally during DNA replication (mitosis) or during meiosis.
Spontaneous mutations
52
____ is the exchange that takes place between a pair of homologous DNA sequences (sister chromatids).
Homologous recombination
53
Are germline mutations inheritable?
YES
54
Which kind of mutation causes no change in the amino acid base?
silent mutation
55
What type of mutation occurs when a purine is substituted for a pyrimidine?
transversion mutation
56
____ mutations occur in sex chromosomes.
Germline
57
What type of DNA repair occurs only in the S and G2 phases?
homologous recombination
58
___ means that genetic information gets scrambled frequently.
Recombination
59
Where does hydrolytic attack occur most frequently on DNA?
at the N-C linkages to the purine ring of the deoxyribose
60
Can DNA information be exchanges through the repair of a replication fork?
YES
61
In what state will the phenotype of a recessive gene be observed?
homozygous
62
The ___ states that genes at different loci are transmitted independently.
Principle of Independent Assortment
63
If each member of a chromosome pair carries the same allele, then that individual is called ____ for that gene.
homozygous
64
Which kind of mutation results in a STOP codon being produced and the protein synthesis halted?
nonsense mutation
65
____ are mobile genetic elements that move in and out of DNA and may interfere with protein coding gene regulation or sequence.
Transposons
66
In the nomenclature of mutations, what does "A1215T" indicate?
that alanine at position 1215 in the protein is changed to a threonine
67
Which base cannot be deaminated?
thymine
68
What type of mutation results in extra or missing amino acids?
deletion or insertion mutation
69
Can mutations that occur in somatic tissues be inherited?
NO - but can give rise to diseases such as cancer
70
In the case of a depurinated A which results in DNA deletion, how many strands will be altered during replication?
one (because the new strand has a deleted base and the new strand is unchanged from the T left behind)
71
What is the genetic exchange between a pair of homologous DNA sequences?
homologous recombination
72
___ alter the structure of DNA and inhibit polymerases and arrest replication.
Premutagenic thymine dimer
73
What is used to measure the distance between two different loci?
a centimorgan
74
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.
Principle of Segregation
75
What does base excision repair involve?
deamination and depurination reactions
76
Can offspring inherit DNA breaks from radiation damage or radioactive chemicals?
YES
77
How is DNA is test tubes renaturized or hybridized?
through a temperature and salt-driven process where high temperatures drives double stranded DNA into single stranded DNA
78
Why is the deamination of 5-methyl cytosine not easily detected as an unnatural base when encountered by DNA repair?
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
Is the damage to DNA repaired accurately in homologous recombination?
YES - damage repaired by using information from a sister chromatid
80
___ are single base differences at a specific position in the genome.
Single nucleotide polymorphisms (SNPs)
81
At what level are SNPs at?
the nucleotide level
82
____ genes have virtually no impact on the trait.
Multigenic
83
In what state will the phenotype of a dominant gene be observed?
heterozygous or homozygous
84
What causes mutations?
spontaneous mutations and induced mutations
85
What happens if there is a loss of proteins needed for DNA repair?
generally lead to lethal events (death to the cell)
86
___ can cause the covalent linkage of two adjacent pyrimidine bases to form thymine dimers.
UV radiation
87
What is an example of a pre-mutagenic lesion?
pyrimidine dimers from UV light
88
What enzyme are unnatural DNA bases recognized and removed by through base excision repair?
DNA glycolase
89
When two DNA strands switch partners between two double helices, this is called a ___.
Holliday junction
90
The loss or alteration of what type of protein often lead to cancer in DNA replication and repair?
accessory proteins
91
What is the mechanism to accurately repair double strand DNA breaks, exchange bits of genetic information, and assures accurate chromosome segregation during meiosis?
homologous recombination
92
____ happens when reactive oxygen species attack the double bonds, CC, or CH bonds on DNA.
Oxidative damage
93
What unnatural DNA base is formed from the deamination of adenine?
hypoxanthine
94
Can pyrimidine dimers be repaired?
yes, by photoreactivation or nucleotide excision repair
95
What type of proteins hold open DNA that cannot survive high temperatures?
DNA binding proteins

Biochemistry (17 decks)

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