Question

how is dna copying essential part of the process of reproduction?

Answer 1

DNA contains information for the inheritance of features from parents to next
generation. DNA presents in nucleus of cells are the information source for making protein.
If information is different, different protein will be made that lead to altered body design.

Answer 2

DNA contains information for the inheritance of characteristics from the parents to the next generation. DNA copying is an essential part of the process of reproduction because it makes possible the transmission of characteristics of the parents to it's offspring in the next generation