If gene duplication didn not occur, how would evolution occur?

Question

If gene duplication didn not occur, how would evolution occur?

Answer 1

Genes do duplicate. When two parents have a baby, both of their genes duplicate. The baby receives some from the father and some from the mother. It does occur. Thats why you'll see some people with the same gene for cancer in one family

Answer 2

it would not.

Gene duplication is the basis of the survival of an specie. If gene duplication did not happen, parents wouldn't have been able to pass their genes to their offspring and therefore the specie would not survive and therefor evolution wouldn't occur either.

Answer 3

A bit slower.  We'd get new genes from viral lysogeny, as well as the getting alternate alleles from other mutations, and we could also get genetic material from the rare endosymbiosis or uptake from the environment.

...and then, of course, the progeny are subject to natural selection.