Consequences of duplication. Results in gene families with two or more loci.
Copies stay same, simply express more product from two copies.
Bacterium Klebsiella aerogenes , selected for growth on new medium, adapted by duplicating a gene that made a useful product but in too low quantities. A single copy couldn't make enough product. One copy inactivated, resulting in a pseudogene. Maybe it got duplicated into a region with no promoter, maybe it accumulated disabling mutations later. A good indicator of a pseudogene is the presence of stop codons in inappropriate places.