 Here students in this module will be talking about comparing sequences from the biological databases. It's a very important module as it will lay the foundation for such an exercise wherein we compare the sequences from different sequence databases. You already know that there are a large number of sequence databases that are available online for you and Gene Bank and Uniprot are two of them. What if I ask you that you take two sequences from one such database and compare them? For instance, if I ask you to take two protein sequences and compare them, what information can this comparison lead us to? One obvious thing is that it can tell you how similar these two sequences are or it can also tell you which specific differences exist between the two sequences. Moreover, it can tell you how the evolutionary process has evolved and how different speciation and differentiation events have occurred in the past. Moreover, it can also help you conclude the relationship between these two sequences. Now let's extend this example to the DNA and RNA sequences as well. You can draw the same conclusions by looking at the sequences from the DNAs as well as the RNAs. Let's consider this sequence and see how such a comparison can be done. In this case, this is the DNA sequence as you can see from the T's. You can simply make it a rule of thumb that if a nucleotide sequence is given to you and it contains T, then it cannot be an RNA sequence. This is a DNA sequence and I want you to compare it with another sequence. Let's consider another sequence A, B, P, G and G. Some obvious difference is that this sequence is longer and this sequence is short as it has only five nucleotides while this has a lot more than five. Secondly, you can easily see that the nucleotide sequence that I mentioned here is similar to the first five nucleotides in the first sequence. This is another information that you can draw. If you want to do a similar comparison with the RNAs, then you have to take an RNA sequence and you can guess that by looking at these uracils here. If I ask you to compare it with U, A, G, E and U, obviously this sequence is shorter again and this one is long but you will see that this sequence matches this portion very nicely. So it is very similar to this sequence but there are two differences here and here so it matches as well but to a lesser degree. The area of the sequence highlighted in red matched perfectly while this portion matched partially. So you can have these very insightful search results by comparing different sequences. Let's consider an example from the proteins. So this sequence is a protein sequence as you can see that it's composed of 20 different alphabets probably and does not limit to A, T, T and G or A, U, D and G. This was the DNA sequence nucleotides these are the RNA sequence nucleotides so this is a protein sequence. So by looking at this protein sequence if I ask you to compare this sequence so you will say that probably this sequence is very close to this portion. However we have three mismatches so here L, F, T exists here I, I, I exist the rest of the sequence matches very nicely M, U, V, K and L but in this case there are three a minor acid mismatches so these are the cases that can exist and these can help you actually as we will see later to look at similarity between sequences the specific differences their evolution as well as the relationship in between the sequences.