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Cell Biology and Genetics > Errors in DNA replication > Flashcards

Errors in DNA replication Flashcards

1
Q

What is DNA replication stress?

A

Inefficient replication

leads to replication fork slowing down, stopping or breaking

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2
Q

What are the causes of DNA replication stress?

A

Defects in enzymes involved

Defects in DNA template strand

Defects in DNA repair pathways

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3
Q

What are some examples of defects in DNA template strand?

A

Transcription occurring during DNA replication

Ribonucleotide included

DNA lesions

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4
Q

What are some examples of DNA replication errors caused by defects in enzymes involved?

A

Slippage

Nucleotide misincorporation

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5
Q

What happens in slippage?

A

Either the template DNA strand or the new DNA strand loops out

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6
Q

What is the consequence of slippage?

A

New DNA strand is either missing a base

or has an extra base

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7
Q

Which increases the risk of slippage?

A

Repeated base

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8
Q

What is nucleotide misincorporation?

A

Incorrect base added to new DNA strand

not complementary

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9
Q

What is responsible for removing mismatched bases?

A

3’ to 5’ exonuclease

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10
Q

What causes nucleotide misincorporation?

A

Defects in 3’ to 5’ exonuclease

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11
Q

What are the types of DNA strand breaks?

A

Single-strand breaks

Double-strand breaks

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12
Q

What is responsible for repairing single-strand breaks?

A

Base-excision repair

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13
Q

What causes single-strand breaks to persist?

A

Defect in base-excision repair

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14
Q

What causes double-strand breaks? How?

A

Single-strand breaks followed by DNA replication

Replication fork reaches break
newly formed DNA molecule breaks off as double-strand

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15
Q

What are the consequences of double-strand breaks in DNA?

A

Lead to translocation mutations
cell death
disease

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16
Q

What do DNA mutations lead to?

A

Cancer

17
Q

What does cell growth inhibition lead to?

A

Ageing

18
Q

What is the cause of Huntington’s disease?

A

Increased number of trinucleotide CAG repeats in Huntington’s gene
produces a protein that gives neurodegeneration

19
Q

What causes the increased number of CAG repeats in Huntington’s disease?

A

Slippage

20
Q

How is Huntington’s disease inherited?

A

Autosomal dominant

21
Q

What does the number of CAG repeats in Huntington’s disease relate to?

A

The age of onset - more CAG repeats means earlier age of onset

23
Q

What is the multi-step cancer model?

A

Refers to how an accumulation of mutations is required to cause cancer

24
Q

What is the cause of Werner syndrome?

A

Mutations in the Werner gene
leads to defects in helicase, DNA replication
DNA damage

24
Q

What does the Werner gene code for?

A

Helicase enzyme involved in DNA replication

24
Q

How is Werner syndrome inherited?

A

Autosomal recessive

26
Q

What is the main symptom of Werner syndrome?

A

Premature ageing

Cell Biology and Genetics (32 decks)

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