Suppose that I wish to find genes involved in leukemia. Following are the steps I would take to search for this information on UniProt:

1. Go to http://www.uniprot.org
2. Choose UniProt Knowledgebase (UniProtKB) in the search field
3. Type "leukemia" in the Query field
4. Click on the Search button
5. You would get around 4000 results
6. Click on the "gene name" link on this page
7. This filter the results by gene name. You would get Q05835.
8. A shorter method is to use "gene:leukemia" in the search field.