We have these purple molecules which are the reverse transcriptase molecules which reverse transcribe the RNA into the DNA. And so when these green molecules, these dark green molecules are injected into that cell, these are the RNA molecules, this purple the reverse transcriptase, the purple enzyme basically creates this lighter green strand which is basically our DNA molecule and then this one also creates a DNA molecule. Those two DNA strands essentially combine to form a double helix DNA molecule and then that goes into the cell and the blue enzyme that integrates molecule now incorporates that into the host genome and that forms the proviral DNA. And now this DNA can be used to synthesize the proteins of interest. Now, a common type of retrovirus that we use when we're dealing with mouse cells is the Maloney urenne leukemia virus. And this is used because it can accept DNA molecules as large as 6000 nucleotides in length.