6.4 Double Helix Structure of DNA

Because “A” always pairs with “T” (and “C” with “G”), these two pairs of nucleotides are always complementary.

If two strands of DNA could be separated (and new DNA be synthesized along these strands), two double-stranded DNA molecules would result, albeit each is an exact copy of the original.

6.4.1 Semi-conservative nature of DNA replication

Figure 6.19: Proof for the Semi-Conservative Nature of DNA

Figure 6.19 demonstrates proof for the semi-conservative nature of DNA replication in the Meselson and Stahl experiment in 1958.

When DNA is copied, the semiconversative nature unwinds the parental strands of DNA. Each strand of DNA is then used as a template for synthesizing a new strand of DNA (a strand that is complementary to the parental strand):

Figure 6.20: Semi-Conservative Nature of DNA Replication

As seen in figure 6.20, two duplexes of DNA would be formed, albeit each duplex has a strand of the original, parental DNA, and the other a strand of new material.