Copying it
1.[2p] After one round of replication in light medium, Meselson and Stahl saw a single band at intermediate density. Which hypothesis did that rule out?
After one round of replication in light medium, Meselson and Stahl saw a single band at intermediate density. Which hypothesis did that rule out?
The answer is: Conservative replication
The answer is: Conservative replication
The answer is: Conservative replication
2.[3p] What did the second generation show?
What did the second generation show?
The answer is: Two bands, half hybrid and half light, which is what semiconservative copying predicts and dispersive copying does not
The answer is: Two bands, half hybrid and half light, which is what semiconservative copying predicts and dispersive copying does not
The answer is: Two bands, half hybrid and half light, which is what semiconservative copying predicts and dispersive copying does not
3.[3p] Why does DNA polymerase synthesise only in the 5' to 3' direction?
Why does DNA polymerase synthesise only in the 5' to 3' direction?
The answer is: The energy comes from the incoming nucleotide, so the growing chain needs a free 3' hydroxyl, and this is also what makes proofreading possible
The answer is: The energy comes from the incoming nucleotide, so the growing chain needs a free 3' hydroxyl, and this is also what makes proofreading possible
The answer is: The energy comes from the incoming nucleotide, so the growing chain needs a free 3' hydroxyl, and this is also what makes proofreading possible
4.[1p] DNA polymerase can begin a new chain from scratch, without a primer.
DNA polymerase can begin a new chain from scratch, without a primer.
The answer is: False
5.[3p] E. coli replicates 4,641,652 base pairs from one origin using two forks at 1000 nucleotides per second. How many minutes does one round take?
E. coli replicates 4,641,652 base pairs from one origin using two forks at 1000 nucleotides per second. How many minutes does one round take?
6.[3p] Match each fidelity mechanism to the improvement it contributes.
Match each fidelity mechanism to the improvement it contributes.
Base selection by the polymerase active site
Proofreading by the 3' to 5' exonuclease
Mismatch repair after the fork has passed
All three together
about one error in
about one error in
a further factor of about 100
a further factor of 100 to 1000
Show the answer
Base selection by the polymerase active site: about one error in Proofreading by the 3' to 5' exonuclease: a further factor of about 100 Mismatch repair after the fork has passed: a further factor of 100 to 1000 All three together: about one error in
7.[2p] At mutations per base per generation across 6.4 billion base pairs, how many new mutations does a child carry?
At mutations per base per generation across 6.4 billion base pairs, how many new mutations does a child carry?
8.[3p] Which are true of telomeres and telomerase?
Which are true of telomeres and telomerase?
Select all that apply
The answer is: The end replication problem arises because the last RNA primer on the lagging strand cannot be replaced, Telomerase carries its own RNA template and writes DNA from it, Telomerase is reactivated in around ninety per cent of human cancers
9.[2p] Why do fluoroquinolone antibiotics and drugs such as etoposide both cause DNA breaks?
Why do fluoroquinolone antibiotics and drugs such as etoposide both cause DNA breaks?
The answer is: They trap a topoisomerase after it has cut the DNA and before it has resealed it
The answer is: They trap a topoisomerase after it has cut the DNA and before it has resealed it
The answer is: They trap a topoisomerase after it has cut the DNA and before it has resealed it