8. DNA repair - safeguarding the genome Flashcards

1
Q

define DNA damage

A

chemical alterations to DNA

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2
Q

define a mutation

A

a change in base pairs

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3
Q

what is a subsitituation mutation

A

a mutation where one codon has been subsituted for another

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4
Q

what is a deletion mutation?

A

when a codon has been removed from a DNA stand and causes a frameshift mutation

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5
Q

what is an insertion mutation?

A

a mutation where a codon is inserted into a strand which causes a frameshift mutation

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6
Q

why dont mutations always get expressed?

A

because misincorporation creates a mutation on the second round of replication

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7
Q

what are the two types of categories of substituation mutation?

A

transition mutations - purine becoming purine and pyrimide becoming pyrimidine

trasversion mutations - purine becoming a pyrimidine and vice versa

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8
Q

how do mutations occur?

A
  • bases that are being mimicked with slight chemical alterations and DNA polymerase dosent recognise the mutation - this is tautomerisms
  • also DNA polymerase comes off the DNA strand
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9
Q

define a Tautomer

A

Tautomers are isomers of an organic compound that exist together in equilibrium and are readily interchanged by migration of an atom or group within the molecule.

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10
Q

why is 5-bromouracil considered a mutagen?

A

it resembles thymine as it has bromine at the same place as the methyl group in thymine so it can be incorporated into DNA.

forms a non-canonical base pair

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11
Q

what does the non canonical base pairing with 5-bromouracil result in?

A

the bromine is highly electronegative, therefore electrons are pulled causing the nitrogen to become a H bond receptor.

This becomes tautomerism

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12
Q

how can tautomerism occur within the body (without mutagens)

think of base pairing

A

due to the resonance strucutrues of adenine, it can result in bonding with cytosine instead of thymine.

results in tautomerism

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13
Q

what is deamination?

A

the removal of an amino group from a molecule

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14
Q

how does deamination create a mutated base pair?

think of a particular base pair deaminated

A

adenine has an amino functional group which can be deaminated therefore loosing the NH3 group, replaced with a C=O bond. this turns adenine to hypoxanthine.

this allows H bonding with cytosine

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15
Q

what is a compound that can increase the chance of deamination?

A

nitrous acid

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