 Dear students, in this module, I'll be introducing you to FAST-A or FAST alignment algorithm. But before we delve into the details of this algorithm, let me take you through the background as to why it is necessary to study FAST-A. So you know that in biological sequence analysis, it is quite a common sight to compare sequences. So these sequences can be DNA, RNA or protein sequences, as you know. And we know several algorithms that are able to compare sequences. The process for comparing these sequences is called alignment, or sequence alignment. Smith-Waterman and Niedelman-Wanch algorithms were used to compare these sequences. Moreover, if you had multiple sequences, then you could use multiple sequence alignment, which is a progressive sequence alignment approach in which you apply pairwise sequence alignment repeatedly or progressively towards creating an overall alignment for multiple sequences. So MSA and pairwise sequence alignment, both of them essentially rely on dynamic programming approaches. Dynamic programming approaches are slow and that they require a lot of computational power. In order for you to compare several sequences, or let's say a database of sequences to some other database of sequences, it will take a lot of time. And if you try to do it by hand, that is, if you try to do Smith-Waterman or Niedelman-Wanch using your mathematical formulations, then it will take a lot of time. In order to expedite things, there are algorithms such as BLAST that are available online. Fast A, or Fast Alignment Algorithm, is also a similar algorithm. So Fast A takes the same approach as was in the BLAST. Fast A was developed in 1988 and the process which it relies on is slightly different from BLAST and is in fact developed earlier than BLAST. So let's take a look at the different web portals that are available for performing Fast A algorithm and to compare sequences. So these will essentially rely on the following concept. We'll discuss the online resources after we understand how these online algorithms or websites they employ Fast A. So towards understanding the basics of Fast A, Fast A extracts regions of absolute identity or 100% similarity. So if you have two sequences, then Fast A tries to find those small regions within one sequence that exists in the other sequence in exactly the same sequence. So once it does that then it can extract those regions or sub sequences and then perform Smith Waterman or Needleman Wunch over the resulting alignment. To elaborate this, so here you have sequences from the database. So obviously in the database you will have several hundreds of thousands of sequences and these sequences can be from DNAs, RNAs or proteins. And then here in blue, if you have the query sequence which may be an unknown sequence or a known sequence, you can find these regions of 100% similar composition with the database. So Fast A finds these regions and employs them in pairwise alignment later. If you want to do Fast A, then you can go to the EBI's Fast A implementation which is available here, ebi.ac.uk slash tools slash SSS slash Fast A. So you will arrive at this webpage and here you can see you have multiple options, proteins, nucleotides, genomes, proteomes, whole genome, shotgun and some other web services. And you can do protein similarity search if you click on the proteins. Similarly, if you click on nucleotides then you have the nucleotide similarity search. So this includes both the DNA sequences and the RNA sequences. And here you can select the database from which you want to obtain the sequences for comparing your query. And of course as I just mentioned, you can also do protein similarity search. The only difference will be that the databases will be the uniprot kb or swiss prot database, protein database. So in conclusion, the Fast A algorithm helps you to perform sequence comparisons in a fast way in a quick way, therefore reducing the computational time that it requires to compare a large number of sequences versus a large sequence database. Also it is available online and you can use it for free.