DNA Polymerase lives and works in the cell’s nucleus where it is the star of DNA replication.
When a cell divides into two cells, it needs to make a copy of its DNA so that each resulting cell has a whole copy. To make sure that the copy is the same as the original, DNA Polymerase reads the code on one DNA strand and strings together DNA pieces (called nucleotides) to make a complimentary DNA strand.
DNA Polymerase is said to have a structure like a hand, with fingers, a thumb, and a palm.
The palm is where the biggest job happens: this is where the new DNA strand is put together. When a DNA piece enters the palm, the fingers close to draw the piece into position. The thumb attracts the new DNA strand so it doesn’t leave before it is completed.
But DNA Polymerase is not just content with a first draft. Getting this job right is key to making sure the cell (and by extension, you!) have the right instructions. Bad instructions could be deadly. So to be extra careful, DNA Polymerase proofreads its work.
When DNA Polymerase makes a mistake, the palm sends the bad DNA away to the proofreading area. There, DNA Polymerase snips off the mistake just like a “backspace” key. Once the mistake is removed, the DNA can move back to the palm where copying resumes.
It is surely a good thing that DNA Polymerase is so careful with its work. It has the important job of conserving the genetic instructions that define life. If it copies the instructions incorrectly in an unlucky part, the cell could lose a critical worker that it literally cannot live without. In reproduction, DNA Polymerase’s diligence in proofreading is responsible for keeping the ova and the sperm viable and preventing genetic diseases in the next generation. What important work!
Julia Migliore 