Example exam questions

What was the initial evidence that DNA carries genetic information in bacteria? How was a role for protein excluded?

Hershey and Chase used bacteriophages to make what fundamental discovery about genes? What was the experimental basis for this discovery?

What are the biochemical properties of DNA polymerases?

Two active sites - one to polymerise, by catalysing the formation of phosphodiester bonds, and one exonuclease cleavage site to remove incorrectly incorporated nucleotides.

What enzymes, apart from DNA polymerase, are needed to synthesise DNA?

• DNA primase

• DNA helicase

• DNA ligase

• Clamp loader

How is DNA replication initiated?

What are Okazaki fragments and what did their discovery tell us about the mechanisms of DNA replication?

Short fragments of DNA, synthesised in the 5’ to 3’ direction on the lagging strand. They are later joined up by ligase. This discovery told us that DNA polymerase synthesises DNA in the 5’ to 3’ direction in both strands.