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Telomeres and Topoisomerases

DNA Damage and Introduction to Mismatch Repair

Announcements:

• The data from this week's lab are now posted. PLEASE NOTE that I need to know from each in vitro group what you loaded in each lane, so I can complete the labeling
• I've changed your lab write-up assignment a bit to reflect this week's results. Details are at the above link.

Learning objectives for Fri 11/17/00

Students should be able to…

1. Define telomere and state why it is important. Describe why telomerase is required to maintain telomere ends and the mechanism by which it achieves this.
2. Define supercoiling, both negative and positive, and explain the advantages and disadvantages of supercoiling. Explain why and how the type I and type II topoisomerases handle supercoils in DNA.
3. State the major forms of DNA damage and their source (exogenous vs endogenous processes). Explain the roles of polymerases and mismatch repair in correcting replication errors.

Outline:

• brief question/answer period on DNA replication material covered in the last class
• compare/contrast prokaryotic and eukaryotic replication
• What are telomeres, and how does telomerase prevent the shortening of telomeres in each cell cycle?
• What is supercoiling, why does it occur, and how is supercoiling resolved during replication?
• What types of damage does DNA accumulate? What is proof-reading? What is mismatch repair?

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