Summary
Summary Tutorial club 3 - Replication & Cell Cycle
- Course
- Institution
Tutorial club 3 - Replication & Cell Cycle
[Show more]
Seller
Follow
rishology
Reviews received
Content preview
Biochemistry and Molecular Biology II – Tutorial club 3: Questions onReplication & Cell Cycle (28-05-18)
BMB2 tutorial (May 2018) DNA metabolism (Lodish 7 Chapter 4)
Q1: (a) What are the known functions of human DNA polymerase and
?
- Pol a: the RNA and DNA primers are necessary, in order for the okazaki-
fragments on the lagging strand to be transcribed.
(b) Which of these polymerases have proofreading activity? DNA pol and
have 3’ → 5’ exonuclease activity.
(c) What happens if DNA pol has an impaired proofreading activity in mice?
There will be a greater risk on mutations to form. Removal of the proofreading
function of DNA pol y leads to loss of mitochondrial functioning which can/will lead to
premature ageing. The concept is that mutant mitochondrial ATP synthetase subunits
generate reactive oxygen species (ROS) that damage the proteome and the nuclear
genome, causing aging.
Q2: a,b,c) Eukaryotes have repair systems that prevent mutations due to
copying errors and exposure to mutagens. What are the three excision-repair
systems found in eukaryotes.
1. Base excision repair (BER) → caused by a deamination of cytosine. Corrects
G-U and G-T mismatches. It removes T and U. Eventually DNA ligase seals
the gap. Should happen before replication. DNA glycosylase flips out the
wrong base. Then APEI endonuclease removes the incorrect base.
2. Mismatch repair (MMR) → This is caused by faulty proofreading. MS2 MS6-
complex recognize the mismatch. DNA helicase unwinds the DNA, allowing an
exonuclease to remove the mismatch. After, DNA polymerase can correct the
mismatch. In the end, DNA ligase seals everything up again and the mismatch
is corrected.
3. Nucleotide excision repair (NER) → Sunlight can cause NERs (UV-radiation
causes thymine-thymine dimers). RNA polymerase II only recognizes NERs
within a gene and the gene has to be transcribed. XP-G and XP-F are two
endonucleases which cut into one strand, in order to remove the damaged
part.
, d) In what way will repair of a transcribed region differ from a non-transcribed
one when it comes to UV-mediated DNA damage? Cell cycle (Lodish 7:
Chapters 19 and 24)
Breaks in the existing (transcribed) region need to be corrected, but it is not known
which bases were in the position to be repaired. Because UV-mediated DNA damage
has an effect on both strands.
*Non-homologous end-joining repair mechanism can be used which repairs double
strand breaks but causes mutations at the repair junction.
The recognition mechanism now occurs by RNA polymerase II and not by XP????
The name XPC comes from xeroderma pigmentosum.
The name CS comes from Cockayne syndrome.
Q3: What is a yeast cdc mutant? Give one example
1. S.pombe (fission yeast)
The benefits of buying summaries with Stuvia:
Guaranteed quality through customer reviews
Stuvia customers have reviewed more than 700,000 summaries. This how you know that you are buying the best documents.
Quick and easy check-out
You can quickly pay through credit card or Stuvia-credit for the summaries. There is no membership needed.
Focus on what matters
Your fellow students write the study notes themselves, which is why the documents are always reliable and up-to-date. This ensures you quickly get to the core!
Frequently asked questions
What do I get when I buy this document?
You get a PDF, available immediately after your purchase. The purchased document is accessible anytime, anywhere and indefinitely through your profile.
Satisfaction guarantee: how does it work?
Our satisfaction guarantee ensures that you always find a study document that suits you well. You fill out a form, and our customer service team takes care of the rest.
Who am I buying these notes from?
Stuvia is a marketplace, so you are not buying this document from us, but from seller rishology. Stuvia facilitates payment to the seller.
Will I be stuck with a subscription?
No, you only buy these notes for $4.28. You're not tied to anything after your purchase.
Can Stuvia be trusted?
4.6 stars on Google & Trustpilot (+1000 reviews)
64450 documents were sold in the last 30 days
Founded in 2010, the go-to place to buy study notes for 15 years now