exam qs lqc 4b

Question 1

explain why Meselson and Stahl accepted one of the models for DNA replication and rejected the other.

Answer 1

the conservative model was rejected and the semi conservative model was accepted, due to the generation 1 has a single band which is halfway between 15^N and 14^N, because the DNA has one strand containing 15^N and one strand containing 14^N, in the semi conservative model further generations would have a band which is halfway between 15^N and 14^N

Question 2

Deduce how many times the bacteria in the culture have divided during this experiment

Answer 2

DNA contents doubles twice, therefore two divisions

Question 3

Explain why the experiment would be improved if all the bases were provided but only the thymine was radioactive.

Answer 3

because thymine is found only in DNA, other radioactive bases taken up by all nucleic acids, only DNA would be measured