CBSE Class 10 Science 2017 · Paper 31/3/C · Question 17

DNA copying: the DNA in the nucleus of a cell is the information source for making proteins. When a cell reproduces, it uses chemical reactions to build a copy of its DNA, so that two copies are formed. This is accompanied by the making of additional cellular apparatus, and the two DNA copies then separate, each with its own cellular apparatus, as the cell divides into two. This is DNA copying. Importance: 1. It is the basic event in reproduction: it passes on the information for making proteins, and so the body design, from parent to offspring. Consistent copying maintains the body-design features that suit the organism to its niche, which keeps populations of the species stable. 2. Copying is not absolutely accurate, so small variations arise in the copies. These variations are the basis of evolution and help a species survive when its niche changes, since some variants may survive conditions that kill the rest.