For more refined maps of genes and DNA segments, consult the NCBI Entrez Genomes division and the Genome Data Base . You must capitalize X and Y to search for those chromosomes. Notice how many different entries the search returned. Multiple entries may be returned because there are many different types of a disease or because multiple genes are involved in the disease. Most diseases are multi-gene disorders involving more than one gene.
Symbol refers to the name of the gene associated with the disorder.
The OMIM number references the OMIM database entry where you can find more information about the disorder. Location tells you which chromosome the gene is located on. For example the first entry below gives a location of 3p21.3. This means the gene is located on the p arm of chromosome 3 at space 21.3. Note that not all disorders listed in OMIM are included on the chromosomes on the HGL Website.