If a DNA sample is not available, can a close determination of a DNA profile be made of that person if there are DNA samples of blood relatives?


If a DNA sample is not available, can a close determination of a DNA profile be made of that person if there are DNA samples of blood relatives?

In: Biology

you’re only able to determine if they are blood relatives if you can compare the two dna samples. without having both samples, it’s not possible.

the way dna profiling works is that you have the dna of the suspect, but don’t know who they are. however, you have another sample that is closely related and you know who they are. so you can use the identity of the known person who is closely related to narrow down who the suspect is.

Parents are like children, due to genetics, because mutations are relatively rare and only two people’s DNA is merged in each generation. So, if you have a sample from someone, their uncle can differ in many fewer ways than an unrelated person. It’s not an exact match, but it can help you prioritize which leads to follow. The colder a case gets, the more you need something like this to get it moving in the right direction.

The odds of your DNA being in the combination it is is about 1 in 400 trillion. So not probable.

Yes. That’s how they caught the golden state killer.

Police collected DNA from the crime scenes but didn’t have a suspect to collect a sample from for comparison. Eventually, they tried comparing the DNA evidence against a database of people who had voluntarily published the results of a home DNA test (like ancestry or 23 and me).

Police got a hit from this database, and upon further investigation determined that the person in the database was not the killer, but was a close blood relative.


Say that John Doe and Jane Doe are siblings.

You have no genetic material from John Doe, but you know his identity and you know that Jane Doe is his sibling, so if you can acquire genetic material from Jane Doe, you will know that John Doe’s genetic profile will be overwhelmingly similar to Jane Doe’s.

There are surely geneticists who will be in possession of the requisite specialist knowledge to elaborate upon *exactly how* John Doe’s genetic material is likely to differ, but for your question the answer is yes; you will be able to determine whether or not genetic material whose provenance is unknown but is suspected to be from John Doe (hence why you’re testing it,) is likely to be a sibling of Jane Doe.

If your question is “can I build a complete genetic profile of John Doe from his sister Jane Doe,” then probably *not,* at least not *exactly.* Maybe if you also have Jim-Bob Joe and Maryanne Joe-Jenkins, the mother and father of John and Jane Doe, and John Doe Jr. the son of John Doe, and Leeroy Doe their older half-brother from Jim-Bob’s previous marriage, and Leeroy Jenkins the mother of Maryanne, you can start to build up a comparative network that will be overwhelmingly close to what John Doe’s actual genetic profile *is,* but that’s pretty excessive and probably unnecessary.