Meselson-Stahl Experiment

Question 1

Summarise the Meselson-Stahl Experiment -

Answer 1

1. Bacteria were fed on medium containing N15.
2. Bacteria then fed on medium containing N14.
3. DNA was extracted from some of the bacteria after one and two generations and was separated by centrifugation
4. at the start there was a single band of heavy DNA.
5. After one generation, there was a single band of intermediate DNA.
6. After 2 generations, there were two bands - one medium and one light.

This proves that DNA replicates semi conservatively.

Question 2

What is conservative replication?

Answer 2

The original DNA molecule remains intact and a new DNA molecule is synthesised that contains no part of the origin;

Question 3

What is semiconservative replication?

Answer 3

Each of the two DNA molecules is composed of one strand from the original molecule and one newly synthesised strand.

Question 4

What its dispersive replication?

Answer 4

Each of the two DNA molecules is composed of sections of the original DNA and newly synthesised DNA randomly interspersed along each strand.