Читать книгу Cell Biology - Stephen R. Bolsover - Страница 87

The genetic material DNA must be faithfully replicated every time a cell divides to ensure that the information encoded in it is passed unaltered to the daughter cells. DNA molecules have to last a long time compared to RNA and protein. The sugar‐phosphate backbone of DNA is a very stable structure because there are no free hydroxyl groups on the sugar – they are all used up in bonds, either to the base or to phosphate. The bases themselves are protected from chemical attack because they are hidden within the DNA double helix. Nevertheless, chemical changes – mutations – do occur in the DNA molecule and cells have had to evolve mechanisms to ensure that mutation is kept to a minimum. Repair systems are essential for both cell survival and to ensure that the correct DNA sequence is passed on to daughter cells. This chapter describes how new DNA molecules are made during chromosome duplication and how the cell acts to correct base changes in DNA.