One success has been the transfer of human insulin genes into bacteria. Ever since the cause of diabetes mellitus was established as a shortage of the hormone insulin, sufferers have been provided with insulin derived from the pan- creases of slaughtered animals. Insulin is a protein, and it was argued that if the genes for this protein could be inserted into a bacterium, then it might be possible to culture the bacterium on a commercial scale and 1 ce it as a more convenient and cheaper source of the hormone. One of the potential problems in transferring genes between eukaryotes and prokaryotes is that different regulatory mechanisms might exist, even if the genes themselves can be transferred, but successful transfer of human insulin genes has now been achieved and commercial production of insulin has already commenced