BLAST is a powerful tool that can be used to compare genetic sequences. BLAST works by comparing a genetic sequence of nucleotides (A, C, G, and T) to a database of sequences.

In the UNIX environment BLAST can easily be installed using the following code:

# Install BLAST
sudo apt-get install ncbi-blast+

Once installed BLAST can be executed from the UNIX terminal. You can either compare your sequences to all the nucleotide data available in the online databases, using the following code:

# Compare query sequences to online databases
blastn -query querySequences.fasta -out blastOutput.txt -db nr -remote

Or you can create a local database on your computer containing the sequences that you are interested in comparing your query sequences against, using the following code:

# Make local database
makeblastdb -in databaseSequences.fasta -parse_seqids -dbtype nucl

With your local database created, you can compare your query sequences against it using the following code:

# Compare sequences to local database
blastn -query querySequences.fasta -out blastOutput.txt -db databaseSequences -outfmt 0