Copy and Paste

Art by Samuel Pilgrim.

Did you know that your body is able to replicate all of the DNA in a cell within an hour and only make three mistakes? Imagine having to copy out all 40 million words of the Encyclopedia Britannica twenty five times over, and making only one error. Even the most astute Oxford student wouldn’t manage such an incredible feat!Bases are the chemical building blocks that make up DNA. Their order on the DNA strand codes the information needed to make everything in your body.  Using the template at the end of the article, try to determine the sequence on the new strand of DNA, given that Adenine (A) pairs with Thymine (T) and Cytosine (C) binds with Guanine (G). It should be fairly simple, but can you do it in 200 milliseconds (1/5th of a second)? Your body can.Yet, even at this impressive speed the replication process would still take about 700 days to copy all three billion bases of the DNA in once cell Instead, your body achieves it in just one hour by initiating replication at multiple sites across the DNA, using biochemical machines called enzymes to carry out specific reactions. DNA polymerases are a group of enzymes that form the new strand by moving along the template strand, adding the complementary bases and, if an error occurs, removing any incorrect bases. As DNA is double-stranded, the strands must first be separated before its bases can be ‘read’. Thus, DNA helicase (another enzyme) unwinds the strands at the speed of a jet engine, allowing enzymes to bind onto them. Enzymes are indeed the biological superheroes that live within us all.