What does semi-conservative replication mean?
Let’s simplify the last diagram, and assume that the whole copying process is complete. The next diagram focusses on the short bit of the total DNA molecule that we have been looking at. A typical human DNA molecule is around 150 million base pairs long – you will have to imagine the rest of it! You have also got to remember that in reality the whole thing would have coiled into its double helix. Trying to draw that just makes everything look messy and complicated! The original DNA is shown all in blue. The red strands in the daughter DNA are the ones which have been built on the original blue strands during the replication process. You can see that each of the daughter molecules is made of half of the original DNA plus a new strand. That’s all “semi-conservative replication” means. Half of the original DNA is conserved (kept) in each of the daughter molecules. The red and blue, of course, have no physical significance apart from as a way of making the diagrams clearer. All three of th
