Students, doing an experiment very similar to the one I demonstrated for the Alu SINE located at the PV92 locus, tested their genotypes at a different locus known as AB21. This locus is polymorphic for the yfg SINE. (Because this is different than the one demonstrated in the video, the sizes of the bands those students observed on their gels will not be the same as the bands shown in the video). The lane marked “C-” is a negative control to make sure no DNA contamination was present in the PCR reactions and “C+” is a positive control. Refer to the AB21 yfg analysis in the gel below to answer the questions that follow.