Tha Matthew Meselson and Franklin Stahl experiment was to prove that DNA replicates semiconservative.It was shown first in Escherichia coli and subsequently in higher organisms, such as plants and human cells .The scheme suggested that the two strands would separate and act as a template for the synthesis of new complementary strands. After the completion of replication, each DNA molecule would have one parental and one newly synthesised strand. This scheme was termed as semiconservative DNA replication . Very similar experiments involving use of radioactive thymidine to detect distribution of newly synthesised DNA in the chromosomes was performed on Vicia faba (faba beans) by Taylor and colleagues in 1958. The experiments proved that the DNA in chromosomes also replicate semiconservatively.

Heavy DNA molecule can be distinguished from the normal DNA by which centrifugation technique ?

 CsCl density gradient .

This heavy DNA molecule could be distinguished from the normal DNA by centrifugation in a cesium chloride (CsCl) density gradient .

In Meselson and Stahl's experiments, heavy DNA was distinguished from normal DNA by centrifugation in CsCl gradient.  When DNA is mixed with caesium chloride it will settle down at based on the density of the DNA sample. Heavier DNA settles down while lighter ones remain above.