A gene that doesn't do anything (like most 'pseudostudents' :-). This might seem odd, and a waste of the organisms time. However, this can be an important evolutionary tool for the genome. By duplicating an existing gene, the pseudogene can mutate as much as it likes while the real copy gets on with doing all the work. In a sense, diploid organisms had(see below) a pseudogenome, since at some stage they duplicated their entire genetic material. Obviously, the genes are now functional - rather than being redundant. This is quite clear in baker's yeast - other creatures (us, for example) have changed so much since then that we cannot survive without both copies (except for diseases that are recessive).

A duplicated gene that is an exact copy of its duplicate is essentially a "dead" gene from the point of view of information. Although it may increase the copy number of the corresponding mRNA's - this may or may not result in more protein. Copies may be promoterless or close to telomeres (which also down regulates transcription).