choose GenBank from the pull down menu and then click "Display" to show the information. For our purpose, however, we want to get the simple DNA sequence, so choose the FASTA format from the same menu and click "Display." Because this gene is huge, for demonstration purposes, select the first few lines of the sequence and copy it.
Now we will use BLAST, the Basic Local Alignment Search Tool, to find other related sequences. To do this, go to the BLAST page at http://www.ncbi.nlm.nih.gov/BLAST/. You will see the many types of BLAST searches that can be performed. There is a BLAST tutorial page at http://www.ncbi.nlm.nih.gov/BLASTinfo/informa-tion3.html. For our example, we will use the Translated BLAST search. This search takes a DNA sequence and translates it into protein sequences. The program can search through the protein database (blastx) or through the DNA database that is translated into protein (tblastx). We will do the latter by clicking on that line and then using the first few lines of our FBN1 gene that we copied by pasting it into the box next to "search." We can leave everything else at the default settings and click on "BLAST." You should now get a box with your request ID and an estimate of the time it will take to do this search. Depending upon how crowded internet traffic is in general and at the NIH site in particular, and depending on the size of your search (which includes both the query DNA sequence length and the database that you are searching), the search can take from seconds to many minutes, and sometimes hours. You can shorten the time needed for your search by using a shorter DNA sequence for the query and limiting your search to a subset of organisms. There are millions of people using this search tool throughout the world, searching through an ever-increasing database. Thus, even the few minutes that a search may take is quite fast!
A BLAST search seeks to find DNA sequences that are similar to the query sequence. The results display the closest match, first in a color-coded graph that shows the region of similarity, ranging from red being the closest match to black being the least similar. The
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