Gene is also often used interchangeably with allele an isoform of a gene as a locus on a chromosome. As far as the Dawkinsite view of evolution goes this is entirely logical. There are also some genes in the mitochondria.
As well as the data segments of genes there are control segments, understanding of which is currently incomplete. In earth biology it is an ordered sequence of nucleotides that encodes a specific biologically active product. In man it is comprised of DNA nucleotides located at a particular position on a particular chromosome unless some forms of mutation have occurred and codes for either RNA or proteins as the functional product.