<P> The conservative hypothesis proposed that the entire DNA molecule acted as a template for the synthesis of an entirely new one . According to this model, histone proteins bind to the DNA, revolving the strand and exposing the nucleotide bases (which normally line the interior) for hydrogen bonding . </P> <P> The dispersive hypothesis is exemplified by a model proposed by Max Delbrück, which attempts to solve the problem of unwinding the two strands of the double helix by a mechanism that breaks the DNA backbone every 10 nucleotides or so, untwists the molecule, and attaches the old strand to the end of the newly synthesized one . This would synthesize the DNA in short pieces alternating from one strand to the other . </P> <P> Each of these three models makes a different prediction about the distribution of the "old" DNA in molecules formed after replication . In the conservative hypothesis, after replication, one molecule is the entirely conserved "old" molecule, and the other is all newly synthesized DNA . The semiconservative hypothesis predicts that each molecule after replication will contain one old and one new strand . The dispersive model predicts that each strand of each new molecule will contain a mixture of old and new DNA . </P> <P> Nitrogen is a major constituent of DNA . N is by far the most abundant isotope of nitrogen, but DNA with the heavier (but non-radioactive) N isotope is also functional . </P>

Which one of these describes how dna is replicated