This explanation assumes that the “Basic Bioinformatics Workflow” has been read.
On the https://blast.ncbi.nlm.nih.gov/Blast.cgi page there is a section for specialized searches. The “Global Align” search can be used to compare two sequences. The search uses the Needleman-Wunsch algorithm.
Let’s try it with human and pig insulin.
Human:
MALWMRLLPLLALLALWGPDPAAAFVNQHLCGSHLVEALYLVCGERGFFYTPKTRREAED
LQVGQVELGGGPGAGSLQPLALEGSLQKRGIVEQCCTSICSLYQLENYCN
Pig:
MALWTRLLPLLALLALWAPAPAQAFVNQHLCGSHLVEALYLVCGERGFFYTPKARREAEN
PQAGAVELGGGLGGLQALALEGPPQKRGIVEQCCTSICSLYQLENYCN
To run the comparison, select “Global Align” from the specialized searches. Then from the top of the search page select “Protein”. Then into the large input boxes (“Query sequence”, “Subject sequence”) copy and paste the human and pig sequences. Then click the “BLAST” button and the search will begin.
Once the search is over, click on the Alignments tab to see a representation of the similarities and differences. Between the sequences, there are matches, mismatches and gaps. Overall, the human and pig sequences are quite similar.
More information about insulin can be found on these pages:
https://www.uniprot.org/uniprot/P01308 (Human)
https://www.uniprot.org/uniprot/P01315 (Pig)
https://en.wikipedia.org/wiki/Insulin
More information about the algorithm:
https://en.wikipedia.org/wiki/Needleman%E2%80%93Wunsch_algorithm
