 Dear students, in this module, we're going to discuss the various types of nucleotides that are there in the DNA and the RNAs. As you would know by now, that the DNA is comprising of four different nucleotides. There are multiple copies of these nucleotides within a single DNA molecule. In case of the RNA, it is also comprised of four different nucleotides and an RNA molecule can have multiple copies of these nucleotides as well. In this figure, you can see that in case of the DNA, you have thymine, adenine, cytosine, and guanine, and they are coupled by sugar and phosphate backbones. To discuss this backbone that is holding the entire nucleotide bases together here as well as on the other strand, let me briefly mention here that the sugars that are there are different in case of RNA and DNA. So you essentially have a sugar, a phosphate, a sugar, a phosphate, and so on which is actually shown here as well. Phosphate is shown by the P while the sugar is shown here. So this backbone differs between the DNA and the RNA by the sugars. So in case of the DNA, the sugars are two deoxyribose while in case of the RNA, it's just the simple ribose. So remember this difference in the sugars between the DNA and the RNA. The coupling to the phosphate stays the same. So it is a phosphate on top of a sugar, on top of another phosphate, on top of another sugar. The nucleotide bases are attached to the sugars. So there are these five different nucleotides if you look at the DNA and the RNA together. So you have adenine and guanine drawn here. So these are termed as the purines due to their structure and then you have the cytosine, uracil, and thymine which are the pyrimidines. So the difference here is in the structure. The purines have two rings while the pyrimidines have a single one. Moreover in case of the DNA, you only have the cytosine, the adenine, guanine, and thymine while in case of RNA, you have adenine, guanine, uracil, and cytosine. So in this way the RNA and DNA differ between uracil and thymine. Now how do these phosphates, sugars, and nitrogenous bases or these nucleotides, they come together? So if you see here carefully, the phosphate group is shown here. The sugar is shown here. In case of RNA, you will have another OH here. In case of the DNA, you will only have a hydrogen here. So on top of this, the nucleotide base comes and attaches itself. So in this way the phosphate, sugar, phosphate, sugar, chain continues and newer nucleotides they come and attach themselves and the DNA or the RNA molecule is constructed. So in conclusion, the DNA gives rise to the RNA and the DNA has four nucleotide bases that is AT, CNG while the RNA has four bases AT, UN, and G. More so DNA is double stranded, RNA is single stranded and the RNA molecule is used towards production of the proteins.