 principles of systematic module 35. In this module, we will discuss molecular and biochemistry characters, how we can use different molecular and biochemical characters for species delimitation or species identification. In this module, different characters have immunological distances, like electrophoretic distances, amino acid sequence variation, DNA hybridization or DNA and RNA sequence differences. So first of all, let's talk about amino acid sequence. If we compare different species and compare proteins in different species, then the sequence of amino acid in the protein is a species which is closely related, then the sequence of amino acid in the protein is very less. But if we compare the amino acid sequence with a distantly related group of the same species, then we can note a clear difference. So the sequence variation in the amino acid can be used to separate the species from one another. Similarly, in different species, the DNA structure and the composition of the nucleotide varies. The DNA structure or the DNA structure can be used to identify the different species and to use this character in species identification. Similarly, in different species, if we compare different proteins, especially the antibodies or the different immunological proteins in all the organisms, then the protein composition of the closely related species is the same and the distantly related organisms have differences. Similarly, if we talk about electrophoretic differences, if we have a sample of different members of different species, when we run the cell and when we compare the proteins' bands, then the same organisms which are closely related match each other's pattern. But the distantly related organisms vary in their protein and band pattern. Although these different species of members have different band patterns, but because all the organisms are basically the origin of the same organism, their ancestors are the same, so there are many proteins in them which are the same and which are conserved. Similarly, the DNA hybridization helps to study the genetic distances in different organisms. On the basis of this technique, we can find genetic variation or genetic similarity. Which organisms are genetically similar and which organisms have more genetic distances and are distantly related to each other? These are the molecular or biochemistry characters which we can identify with the help of which species. We can compare their protein, their electrophoretic profile, their DNA and RNA, we can study the similarities and differences in them. Similarly, we can compare the genetic distances in the organisms and we can see whether they are the same or distantly related.