2, 4, 6

You proceed to sacrifice mice 2, 4 and 6, which you believe do not carry the transgene. Your supervisor sees you heading down to the animal facility and asks to see the results of your PCR experiment. Dr Demetriou asks you to reconsider your interpretation of the results. He reminds you that the absence of a band signifies a mouse that does not carry the transgene. However, band widths can vary.