Polymerase Errors, Mutations, and DNA Repair Mechanisms

These flashcards cover key concepts about DNA polymerase, mutations, and DNA repair mechanisms.

What are the two main characteristics of DNA Polymerase (DNApol)?

(1) Processivity (2) Fidelity (proof-reading function)

What is processivity in the context of DNA Polymerase?

The average number of nucleotides added each time the enzyme binds a template.

How do nonprocessive DNA polymerases differ from processive DNA polymerases?

Nonprocessive DNA polymerases add nucleotides at a rate of one nucleotide per second, while processive DNA polymerases can add multiple nucleotides per second.

What is the proof-reading function of DNApol III?

DNApol III has exonuclease activity that chews back (3’ to 5’) to remove mismatched nucleotides.

What are spontaneous mutations?

Mutations resulting from the nature and structure of DNA.

What is depurination?

The breaking of the bond between a purine base (A or G) and its ribose sugar.

What happens during deamination in DNA?

The loss of an amino group from cytosine, converting it to Uracil.

What is a consequence of methylated cytosine undergoing deamination?

It converts to Thymine, which will NOT be recognized by DNA repair mechanisms and leads to substitutions.

What does a tautomeric shift lead to in terms of DNA mutations?

It leads to improper base-pairing, which can cause substitutions.

What is oxidative stress in relation to DNA?

Damage caused by Reactive Oxygen Species (ROS) which can convert Guanine (G) to 8-oxoG.

What is the effect of 8-oxoG during DNA replication?

8-oxoG pairs with Adenine (A) during replication.

What are tri-nucleotide repeats?

Regions in DNA that can lead to expansions as DNApol tries to read through hairpin loops.

What are the types of induced mutations?

1) Base modifications 2) Intercalating agents 3) Base analogs 4) Ionizing radiation 5) Non-ionizing radiation.

How do intercalating agents like acridine orange affect DNA?

They can lead to insertions or deletions of single nucleotides.

What is a base analog mutation involving 5-bromouracil?

It is incorporated as a Uracil but base pairs with Adenine (A) or Guanine (G).

What are the effects of ionizing radiation on DNA?

It produces free radicals within tissues, leading to base deletions and breaks.

What kind of damage does UV-light radiation cause?

It produces Thymine dimers.