So let's take a look at each one of these post transcriptional modifications of the mRNA and see what they are and why they actually take place. And let's begin with the addition of the five and guanosine triphosphate cap. So within the nucleus of the cell, before our pre mRNA actually leaves the nucleus the five end of the precursor mRNA is altered by the attachment or the addition of a guanacine nucleotide via a special type of bond, a special type of linkage known as the five to five triphosphate linkage. And following the additional detachment of this cap the guanacine nucleotide is also altered in several ways. One of the ways in which the guanacinucleotide is altered is by the methylation of the seven position to form the seven methyl guanosine nucleotide. So this type of five guanosine triphosphate cap is shown in the diagram.