Lecture 5-7 DNA replication

Question 1

Define what semi-conservative means in respect to replication

Answer 1

It means that a double strand seperates into single strands and acts as templates and the required opposite strands attach to give two identical double strands. Found by Meselson and Stahl. One new strand one old strand.

Question 2

Describe experiment that shows replication is bi-directional

Answer 2

3H - thymidine experiment grew E.coli in medium to low specific activity 3H - Thymidine (low level of 3H) and just before harvest added very high 3H - thymidine activity. Origin grew both ways (in replication forks).

Question 3

Role of DNA polymerase I

Answer 3

Has 5’ exonuclease activity, which removes the RNA primers and then synthesizes DNA when primers ar eremoved