 So, now we study the prokaryotic genome, prokaryotes are the organisms in which the DNA is not enclosed in membranes, so there is no nucleus, so as there is no nucleus there are no justification to have other membrane bound organelles, so these are relatively simple cells. Here in this diagram we see a prokaryotic cell which is a bacteria right here, so we have the genome, the DNA in the shape of a big chromosome in the middle and ribosomes small structures obviously protein senses is needed for every organism, so ribosomes are also there and then we have a relatively simple cell and then we have its walls or different layers. Here we see a comparison between a eukaryotic cell and a prokaryotic cell, so as we see in these circles we have all those membrane bound organelles which are present, one of them is mitochondria, so that is involved with the respiration process, so in which the food is broken down into the energy, so there is a hypothesis that this mitochondria actually evolved from a bacteria, that hypothesis is called as endosymbiont hypothesis, so here is a comparison between the sizes also, so eukaryotic cells are complex and bigger than prokaryotes. So, the first prokaryotic organism that was sequenced was humophilus influenzae, we have seen that in a previous section, so that was the organism that was sequenced in relatively moderate cost and with an efficient pace and it papped away for sequencing of the other organisms, so those study of those prokaryotic organisms is important. So, there are different criteria for selection of those organisms to be sent into a genome sequencing project, so for most important them is that there might have been intensive studies on that organism, so it has been a model organism and that has been investigated in details, it might be important human pathogen, so that is why we are studying its genome, it might have some phylogenetic importance and the sequences were annotated as they were sequenced. So, here in this diagram we see different prokaryotic organisms, representative prokaryotic organisms and their genomes, this E. coli that was sequenced by Blackner et al, so that has a genome size, so we see its phylogenetic group also, it is a bacteria, then in this set we have just one archaea and we have rest of them which are bacteria, so genome size is 4.6 MBs and number of protein coding sequences are there in this parenthesis, so they were 4000 genes in this organism. Then archaea methanococcus that is 1.66 MB and it has 1682 genes, then we have hemophilus influenzae 1.83 MB and 1743, it is a human pathogen, we can also have descriptions of these organisms like E. coli is a model organism and then obviously this archaea it grows at high temperatures and it produces methane, maybe go to have natural gas from it, we can also have other organisms like mycoplasma, pneumoniae, pathogens obviously. It was 0.82 MB and 676 genes and then we have in the end we have this syncosystis that is a bacteria, so that is 3.57 MB and it has 3168 genes, so prokaryotes are simple genomes, easy they are easy models to study the biochemistry and physiology of life and then sequencing is normally done on these simple genomes first and then it helps exploring the complex genomes.