BIOC0007 DNA REPAIR EXAM QUESTIONS AND
ANSWERS WITH COMPLETE SOLUTIONS VERIFIED
What is endonuclease?
An enzyme that cleaves the phosphodiester bond within a polynucleotide chain, often
used in DNA repair to remove damaged sections.
How many DNA errors occur daily in every human cell?
Between 10,000 to 1 million DNA errors occur daily in every human cell.
What is the role of DNA repair systems in cellular health?
they correct the frequent errors that occur in DNA, thereby maintaining cellular integrity
and preventing mutations from becoming permanent.
How do mutation rates vary across the chromosome?
some sites acting as hotspots where mutations occur at a high frequency, while other
sites undergo alterations less frequently.
Why is the integrity of the DNA replication process important?
The integrity of the DNA replication process is crucial for preventing errors that can lead
to mutations and cellular dysfunction, ensuring accurate genetic information is passed
to new cells.
How does MMR repair system work?
MMR corrects mismatches that escape the DNA polymerase proofreading activity
during replication. These mismatches might include incorrect bases that have been
incorporated into the newly synthesized DNA strand.
,1. MutS protein recognizes and binds to the mismatch in the DNA. MutL then binds to
MutS, stabilizing the formation of a MutS-MutL complex.
2. The complex interacts with MutH, which is attracted to hemi-methylated sites (where
the parent strand is methylated and the new strand is not). This recognition is crucial as
it identifies the newly synthesized strand which needs correction.
3. MutH cleaves the newly synthesized strand at a GATC sequence near the mismatch.
4, Helicase unwinds the DNA starting at the cleavage site. DNA exonuclease then
removes the segment of the DNA containing the mismatch from the cleavage site up to
the point of the mismatch.
5. DNA polymerase (like Polymerase III in E. coli) fills in the gap with the correct
nucleotides using the parent strand as a template. DNA ligase then seals the strand by
catalyzing the formation of phosphodiester bonds between adjacent nucleotides,
finalizing the repair.
what are the participants in MMR system
3x mut protein (Mut S, L, H), DNA polymerase, helicase, exonuclease, ligase
What is the acronym for MMR system?
Scientists Love Helping Heal Every Patient's Lungs
what is methylated site sequence?
, GATC
MMR involving mut protein are ?
mismatch that evaded dna polymerase proofreading activity
post replication MMR
Post relication MMR repairs damage generated during DNA replication using DNA
polymerase proofreading activity.
The mismatch generated every 10^-10 in high fidelity polymerase will have suboptimum
energy/geometry configuration that alerts the reliposome.
The sequence will pause and transfer the 3' end of the growing end back to its
exonuclease site to excise the mismatch
the mismatch will be replaced by the correct complementary base at the catalytic site of
the primer template junction.
The replication process can now continue without risks of carrying faulty genetic
information.
what does the replisome contains
dna polymerase, primase, ssb, clamp loader, sliding clamp, helicase
DNA damage can be induced by either ( ) or ( )
normal cellular processes, or environmental factors
What are example of DNA damage induced by normal cellular processes?
ANSWERS WITH COMPLETE SOLUTIONS VERIFIED
What is endonuclease?
An enzyme that cleaves the phosphodiester bond within a polynucleotide chain, often
used in DNA repair to remove damaged sections.
How many DNA errors occur daily in every human cell?
Between 10,000 to 1 million DNA errors occur daily in every human cell.
What is the role of DNA repair systems in cellular health?
they correct the frequent errors that occur in DNA, thereby maintaining cellular integrity
and preventing mutations from becoming permanent.
How do mutation rates vary across the chromosome?
some sites acting as hotspots where mutations occur at a high frequency, while other
sites undergo alterations less frequently.
Why is the integrity of the DNA replication process important?
The integrity of the DNA replication process is crucial for preventing errors that can lead
to mutations and cellular dysfunction, ensuring accurate genetic information is passed
to new cells.
How does MMR repair system work?
MMR corrects mismatches that escape the DNA polymerase proofreading activity
during replication. These mismatches might include incorrect bases that have been
incorporated into the newly synthesized DNA strand.
,1. MutS protein recognizes and binds to the mismatch in the DNA. MutL then binds to
MutS, stabilizing the formation of a MutS-MutL complex.
2. The complex interacts with MutH, which is attracted to hemi-methylated sites (where
the parent strand is methylated and the new strand is not). This recognition is crucial as
it identifies the newly synthesized strand which needs correction.
3. MutH cleaves the newly synthesized strand at a GATC sequence near the mismatch.
4, Helicase unwinds the DNA starting at the cleavage site. DNA exonuclease then
removes the segment of the DNA containing the mismatch from the cleavage site up to
the point of the mismatch.
5. DNA polymerase (like Polymerase III in E. coli) fills in the gap with the correct
nucleotides using the parent strand as a template. DNA ligase then seals the strand by
catalyzing the formation of phosphodiester bonds between adjacent nucleotides,
finalizing the repair.
what are the participants in MMR system
3x mut protein (Mut S, L, H), DNA polymerase, helicase, exonuclease, ligase
What is the acronym for MMR system?
Scientists Love Helping Heal Every Patient's Lungs
what is methylated site sequence?
, GATC
MMR involving mut protein are ?
mismatch that evaded dna polymerase proofreading activity
post replication MMR
Post relication MMR repairs damage generated during DNA replication using DNA
polymerase proofreading activity.
The mismatch generated every 10^-10 in high fidelity polymerase will have suboptimum
energy/geometry configuration that alerts the reliposome.
The sequence will pause and transfer the 3' end of the growing end back to its
exonuclease site to excise the mismatch
the mismatch will be replaced by the correct complementary base at the catalytic site of
the primer template junction.
The replication process can now continue without risks of carrying faulty genetic
information.
what does the replisome contains
dna polymerase, primase, ssb, clamp loader, sliding clamp, helicase
DNA damage can be induced by either ( ) or ( )
normal cellular processes, or environmental factors
What are example of DNA damage induced by normal cellular processes?
