 Dear students, this is the first chapter in our course and it will be about the sequence analysis. Before we delve into this topic in detail, we need to understand the different types of sequences that are output from biological experiments. These include the DNA sequences, the RNA sequences, the protein sequences and so on. So let's take a look at how this information is organized and the sequences are obtained. You know that all living things are composed of cells and at the heart of each cell lies its DNA. The DNA is responsible for the creation of a cell and its lifespan as well. The maintenance of these cells during their lifespan are also totally dependent upon the DNA sequence inside the nucleus in case of eukaryotes. Next, this blueprint that is provided by the DNA, it gets transformed into RNAs and proteins. This constitutes the central dogma in biology. The transformation of the DNA is firstly into an RNA sequence. This is followed by the conversion of the RNA sequence into a protein and the proteins in turn they form the various organelles within the cell as well as its membrane. Let's take a look at how this information is transferred. As you can see here, the DNA it is encoding for an RNA and the RNA is encoding for the proteins. The proteins they form the cells, the membrane of the cell, the organelles within each cell and the other signaling molecules between the cells. This is termed as the central dogma and the flow of information between the DNA to RNA to proteins is defined as the central dogma. If you look at the DNA then two things are obvious. The first thing is its double helical structure that is one strand of nucleotides are running in parallel to a second strand. Secondly, these two strands are held together by different base pairs as indicated by the colored lines. If you look at it closely then this resembles a phosphate and a sugar. A phosphate and a sugar lined upon each other on each strand in the anti-parallel direction and the nucleotides T, A, C, T are coupled with Y, G, T and A. Once these nucleotides they come together they hold the two strands in a helical conformation and you end up with the helical DNA. Next the information from DNA encodes for an RNA. The RNA molecules are single stranded as shown here and the nucleotides are unpaired as you can see in the figure in front of you. So once you want to transform the DNA into an RNA you have to open this DNA sequence into two strands and the complementary strand is copied. Another difference is that in the DNA you have thymine as indicated by T while in the RNA you have uracil as indicated by U here. Important to note that C is complementary to G while A is complementary to U. So this is how the DNA is transformed into the RNA and next the RNA encodes for some amino acids for 20 amino acids which come together in the form of this chain and after a process called folding the proteins take their 3D shape. We will look at it in detail in later modules as well. And the proteins in the end they constitute the cell and the various organelles within the cells as shown here. So in conclusion DNA codes for an RNA and the RNA encodes for a protein while the protein goes and constitutes the various organelles and membranes of the cells.