The search for genes in a genome could include some inaccuracies due to the presence of non-genes which have some features of a gene that a computer might mistake for signs of a gene. These could include pseudogenes, non-functional copies of what had once been functional genes, and other similar genetic phenomena.
Work Step by Step
The computer search would only look for characteristic sequences, not for actual function, which is how these errors could occur. Results could be improved by doing a more precise search or by having a researcher check that true genes with all of the normal features of eukaryotic genes were the things being counted.