Many sources say that genes are regions of DNA which store information used to code for proteins. While it is true that many genes store information used to code for proteins, it is not true that all genes store information used to build proteins.
The modern definition of gene is a region of DNA which is transcribed. This includes genes in the tRNA and rRNA families. These DNA regions are transcribed to produce molecules of transfer RNA and ribosomal DNA.
The three domain classification system (eukaryota, bacteria and archaea) proposed by Carl Woese in 1977 is based upon sequence data of rRNA genes.
This video provides a review of how information in a gene that codes for a protein is retrieved and used by cells.
Hope this helps!