For her senior project at Portland Adventist Academy (PAA), Cassie Lemke did DNA testing on three sets of twins to determine if they were identical or fraternal (non-identical). She found, to the surprise of many, that one set of similar-looking twins were apparently not identical. A second set was confirmed as identical, and a third set was indeterminate because they were missing the gene that she tested.

Lemke plans to become a forensic scientist and explains that much of forensics relies on DNA testing. As part of her project, she shadowed two licensed forensic scientists in their lab, observing, doing simple specimen sampling and making log entries. Lemke also did some preparatory work and observed the testing of specimens from a high-profile rape investigation.

Lemke states that to absolutely confirm whether twins are identical or not, at least three genes are usually tested for their location on a chromosome. Because of budget considerations, she could only test for one gene, so her results are only suggestive.

PAA is one of the few secondary schools with equipment for DNA studies. Lemke learned how to split chromosomes, incubate the genes and do gel diffusion to identify the location for the gene.

Lemke presented her findings at PAA’s annual educational expo.