This video provides a step-by-step tutorial on how to run a similarity search using the web interface of the Ensembl BLAST and BLAT tools. Denise from Ensembl Outreach has got a human DNA sequence, which is 3 kb long, and wants to find out where it maps on the human genome. If you want to replicate her results, whether or not you are new to the BLAST and BLAT tools in Ensembl, Denise's query sequence can be found on http://bit.ly/1rum5J7