Lecture 6: DNA Replication and Translation Flashcards
What is an autocatalytic process?
A process in which the product of the reaction serves as a catalyst for said reaction.
Why are certain genes so highly conserved?
These genes were developed in an early ancestor, and do not require genetic mutation, such as ribosomes.
Why does DNA have 3’ and 5’?
Because the ribose sugar binds a phosphate on its 5th carbon and 3rd carbon, and this determines the direction of the strand.
What is the difference between how DNA is replicated on the leading strand and the lagging strand?
The leading strand is replicated all in one go, the lagging strand is replicated in chunks (Okazaki fragments).
What are Okazaki fragments?
Short sections of DNA that are synthesised on the lagging strand (3’ to 5’).
How are Okazaki fragments created?
- DNA primase synthesises RNA primer to start replication when polymerase finishes and releases previous
fragment, removing single strand binding proteins. - Helicase unwinds the strand more until a loop is formed and primer lines up with polymerase.
- Once DNA polymerase finishes, RNase digests the primer.
- The fragment is bound to the existing chain by DNA ligase, forcing polymerase to release the strand from a loop and beginning the process again.
What is telomerase and how does it work?
How was telomere length concluded to be highly controlled?
By experimenting with yeast cells, short and long telomeres were added and over several generations the telomere length would eventually return to standard telomere length.
What correlation does telomerase have with tumour survival?
Why does this happen?
When TA presence is high, cancer cell survival is higher.
This happens because
What do T-loops in telomeres do?
Allows the body to distinguish telomeres from a DNA-ds break.
What is the error rate of polymerase?
1 in 1x10^5
What mechanisms reduce final error rate? By how much?
Final error rate is 1x10^10.
This is achieved by proofreading mechanisms and mismatch repair mechanisms.
What is thought to contribute to DNA mismatch?
Tautomers of bases (forms of bases that change back and forth in phase action). These tautomers will cause errors in polymerase reading.
What is polymerase proofreading activity?
How does mismatch repair occur?
