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BIOL308 Study Guide - Final Guide: Ap Endonuclease, Apoptosis, Glycosidic Bond

6 pages100 viewsSpring 2018

Course Code
Dragana Miskovic
Study Guide

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1. Distinguish between the terms “mutation”, “DNA repair” and
Mutation is a change in DNA sequence that may or may not alter protein
DNA repair is the repair of damaged dna that contains errors to increase fidelity
but also decrease variability
Recombination is the exchange of genetic information between two molecules of
dna in order to increase variability.
Dna repair
2. List and briefly explain three major causes for mutation in DNA.
Replication error incorrect nucleotides incorporated into strand that were not
detected by mistmatch repair
Spontaneous dna change deamination and depurations, deamination of cytoi
External factors (UV Light), adition of alkyl groups to dna bases
3. Explain how errors in DNA replication can lead to mutations.
During dna replication, mismatched nucleotide may be incorporated, dnap
proofreading does not catch this error, leads to a change in nucleotide sequence,
which can lead to change in
4. Distinguish between the effects of mutations on the somatic and germ
cells of multicellular organism.
If a mutation occurs in a somatic cell, the mutation would not be hereditary, could
elad to cancer
If mutation occurs in germ cell, mutation could now be hereditary and inherited by
daughter cells and future progeny.
5. List the various types of DNA repair mechanism (we have mentioned
Endonuclease acitivty of polymeras
Base excision
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Nucleotide excision
Direct reversal
Error prone
Mismatch repair
6. Give the detailed description of the base excision (or nucleotide excision)
repair process in bacteria.
Glycosylase recognizes and removes damaged base by hydrolyzing glycosidic
AP endonuclease removes abasic sugar
DNA polymerase fills with correct base, ligase seals nick
NE repair UVR ab scan strand until damage is detected by uvr a causing uvr b
to recruit uvr c which makes nick on the strand allowing uvr d to act as helicase
and unwinds strands so that dna pol I can excise and repair damage
7. Describe the mismatch repair process of bacteria (pay attention at the
ways in which the daughter and parent strand are recognized by repair
MutS scans for distortion, binds to mismatch, MutL recruited by muts to
transolacte along dna until dna initiation sequence GATC, binds to GATC
sequence to form a loop of DNA, MUTSL complex activates mut h which has
endonuclease activity, nicks unmethylated strand (the one that was laid down
more recent so will have the mismatch), strand degraded from mismatch to gatc
sequence, new strand is synthesize with dna pol III
8. Describe briefly the mechanism of direct reversal of damage in bacteria.
Can be done when thymine dimers form from UV damage, photoreactivation,
done by photolyase, breaks covalent bonds between thymines
9. Distinguish between the two DSB repair mechanisms we talked about in
Recmobination and Non homologous end joining
Recombinatnion, mode of fillingin gap of one strand of a duplex by retrieving a
strand from a homologes dupblex. Replication fork reaches nick, breaks down,
strand breaks off, 5’ end is degraded to form 3’ overhand, invades another
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