Officials at the Pentagon have told reporters that DNA compared with Osama bin Laden’s relatives confirmed his death. But so far, no one knows which samples were used or even what type of genetic tests were conducted.

Best case scenario: The government somehow collected DNA samples from bin Laden at a different time before he died.

But this doesn’t seem to be the case.

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Since humans share more DNA with their immediate relatives, it’s possible to show relatedness by comparing samples with those of family. Comparing bin Laden’s DNA to that of his parents or children would produce the second strongest results. Some sources state that bin Laden’s son was also killed in the raid, as reported by The Washington Post. If this was the case, the genetic comparison may have helped ID bin Laden — after they confirmed the identity of his son first.

Another way of IDing the man behind 9/11 is comparing bin Laden’s DNA with that of his half-siblings.

Initially, word spread that scientists used brain tissue from his half-sister, who allegedly died of cancer in a Boston hospital. Rumors amassed that portions of her brain had been subpoenaed for the analysis.

Yet no such records could be confirmed at the Massachusetts General Hospital, where she supposedly received treatment and succumbed to cancer, according to The New York Times.

Still, others questioned the feasibility of conducting DNA sequencing and typing within a short amount of time. But with the right resources (which the government has), the process can easily be done within a matter of hours.

Genetic sequencing relies on extracting DNA from samples to amplify. Genetic material may come from many sources such as hair, blood or even cells from inside one’s mouth. All that’s needed is one cell with the DNA in good shape. Scientists commonly use a method called polymerase chain reaction (PCR) to create copies of a specific part of DNA. Polymerase helps coax DNA to replicate itself, leaving researchers with large numbers of samples to work with.

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Next, scientists look at tandem repeats, or the repeat of two or more nucleotides, in roughly 13 to 15 regions of a DNA sample called loci. This process helps create a DNA fingerprint that can be compared to other samples to measure relatedness.

After lining up the results, researchers can make strong statements about the genetic relatedness of the people whose DNA samples are being profiled.

More specifics of the process as well as how long it takes are by science writer Christie Wilcox in a Scientific American blog post.

It’s possible scientists could have looked at genetic similarities in the mitochondria or even Y chromosome of samples as well, depending on what’s available to test.

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