# Can scientists determine whether a DNA sample is from a human being? **URL:** \ **Category:** Factual Questions\ **Created:** [January 22, 2003, 6:11pm UTC](https://boards.straightdope.com/t/can-scientists-determine-whether-a-dna-sample-is-from-a-human-being/150263 "2003-01-22T18:11:05Z")\ **Posts on this page:** 12\ **Page:** 2
**Author:** ![Smeghead](https://avatars.discourse-cdn.com/v4/letter/s/f1d935/32.png) [@Smeghead](https://boards.straightdope.com/u/Smeghead)\ **Post date:** [January 22, 2003, 11:44pm UTC](https://boards.straightdope.com/t/can-scientists-determine-whether-a-dna-sample-is-from-a-human-being/150263/21 "2003-01-22T23:44:31Z")
> [@](#): > > \*Originally posted by vibrotronica \* > \*\* > Could the common PCR or RFLP tests distinguish me from my non-twin brother? My sister? My half-brother or -sister, either with the same mother or father? > … > Would a DNA test be able to tell the difference? \*\* Yes, yes, yes, and yes. It all depends on which primers you choose to use, and what part of the DNA you want to amplify. ---
**Author:** ![Derleth](https://avatars.discourse-cdn.com/v4/letter/d/b9e5f3/32.png) [@Derleth](https://boards.straightdope.com/u/Derleth)\ **Post date:** [January 23, 2003, 2:26am UTC](https://boards.straightdope.com/t/can-scientists-determine-whether-a-dna-sample-is-from-a-human-being/150263/22 "2003-01-23T02:26:55Z")
OK, just so I don’t have to wade through the bullshit after Googling, what does karyotype _really_ mean in a biological context? ---
**Author:** ![Stan\_Doubt](https://avatars.discourse-cdn.com/v4/letter/s/53a042/32.png) [@Stan\_Doubt](https://boards.straightdope.com/u/Stan_Doubt)\ **Post date:** [January 23, 2003, 3:38am UTC](https://boards.straightdope.com/t/can-scientists-determine-whether-a-dna-sample-is-from-a-human-being/150263/23 "2003-01-23T03:38:05Z")
A karyotype is a picture taken of a cell’s nucleus where the chromosomes (tightly bundled strands of chromatin) are visible. It is usually taken during the beginning stage of mitosis and a stain may be used to highlight the chromosomes. In a good karyotype, you can differentiate each individual chromosome. Given three karyotypes, one from a human, one dog and one fruit fly, it is easy to tell which karyotype belongs to which animal based on the number of chromosomes. Karyotypes may be used to detect the sex of an individual, and even diseases related to chromosome number, e.g., Klinefelter’s Syndrome. ---
**Author:** ![dauerbach](https://avatars.discourse-cdn.com/v4/letter/d/c2a13f/32.png) [@dauerbach](https://boards.straightdope.com/u/dauerbach)\ **Post date:** [January 23, 2003, 2:09pm UTC](https://boards.straightdope.com/t/can-scientists-determine-whether-a-dna-sample-is-from-a-human-being/150263/24 "2003-01-23T14:09:46Z")
They don’t give species information in and of themselves. However, they can be used to identify species when used in conjunction with a data bank. Here is an example of using PCR to determine the species of a sample of tuna. This isn’t really determining the species of tuna de novo, but rather comparing the electrophoresis pattern with knowns. As such it is identical to the way DNA fingerprinting is used in humans. Throw human or simian DNA into the array and all you will know that it is not from one of the given species of tuna. You will not know if it is mammalian, reptilian, fish, etc. Perhaps, if you had human and simian standards, and carefully chose the restriction enzymes you could differentiate human from ape, but I still question even that. Most of the differences in the two genomes would be histocompatability sites, with perhaps a HOX or two different, but since the technology is really comparing junk stretches of the genome I still doubt that you could differentiate the two. Karyotype would easily do it, I am still looking for cites to support my contention that fingerprinting would not. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [January 23, 2003, 3:27pm UTC](https://boards.straightdope.com/t/can-scientists-determine-whether-a-dna-sample-is-from-a-human-being/150263/25 "2003-01-23T15:27:01Z")
**dauerbach** , I think you are simply arguing semantics at this point. We _do_ have human and simian standards for comparison, and given this a given sample could be identified as being from one or the other (or from neither). This is the question posed by the OP, not whether a sample could be identified without comparison. In any case, you have the same problem with karyotype - unless you have a reference to compare it to in detail, all you can say is that the sample does or does not have a particular chromosome number or morphology. This in itself does not give any more information about species identity than DNA analysis does. ---
**Author:** ![dauerbach](https://avatars.discourse-cdn.com/v4/letter/d/c2a13f/32.png) [@dauerbach](https://boards.straightdope.com/u/dauerbach)\ **Post date:** [January 23, 2003, 4:44pm UTC](https://boards.straightdope.com/t/can-scientists-determine-whether-a-dna-sample-is-from-a-human-being/150263/26 "2003-01-23T16:44:36Z")
Colibri, I don’t think we are arguing semantics. I look at the question like this: You find blood or semen or whatever at a crime scene. You process the sample and run it through any type of DNA fingerprinting routine you want. Is there any way to determine that the DNA is from an ape. I say no. If you are allowed to look at the karyotype I say why bother, just look at the criminal. If it is an ape it would be readily apparent. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [January 23, 2003, 6:24pm UTC](https://boards.straightdope.com/t/can-scientists-determine-whether-a-dna-sample-is-from-a-human-being/150263/27 "2003-01-23T18:24:11Z")
> [@](#): > > \*Originally posted by dauerbach \* > \*\*You find blood or semen or whatever at a crime scene. You process the sample and run it through any type of DNA fingerprinting routine you want. Is there any way to determine that the DNA is from an ape. I say no. \*\* Well, then, all I can say is you are incorrect. I have already provided an example of how PCR can be used for species identification in tuna. Similar techniques could be used to match simian DNA to species, or at least to conclude that it’s simian rather than some other taxon. The OP is not concerned with whether species IDs can be made de novo, but whether they can be made at all. ---
**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\ **Post date:** [January 23, 2003, 6:26pm UTC](https://boards.straightdope.com/t/can-scientists-determine-whether-a-dna-sample-is-from-a-human-being/150263/28 "2003-01-23T18:26:50Z")
No, that’s not correct. It is true that you couldn’t tell it was ape blood just by looking at it, or random DNA tests. But if you suspected it was ape blood, you could compare the DNA of the blood sample to a blood sample taken from a known source, a chimpanzee. You absolutely CAN determine which species provided the blood. Currently I believe it would require a brute force approach to determine the species. First you test if it is a chimpanzee. If not, test if it is a gorilla. If not test if it is an orangutan. If not, test if it is a siamang. Of course, these tests are really done in reverse, just like the paternity tests they do on Montel Williams. They can tell you absolutely that the specimen is NOT from such and such a person, or from such and such a species. Do that often enough from enough loci and you can get any arbitrary confidence level that it IS from a specific person or species that you want. ---
**Author:** ![dauerbach](https://avatars.discourse-cdn.com/v4/letter/d/c2a13f/32.png) [@dauerbach](https://boards.straightdope.com/u/dauerbach)\ **Post date:** [January 23, 2003, 7:20pm UTC](https://boards.straightdope.com/t/can-scientists-determine-whether-a-dna-sample-is-from-a-human-being/150263/29 "2003-01-23T19:20:20Z")
Ok, I tried to find this on the web and could not. Could I have some cites please. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [January 23, 2003, 7:36pm UTC](https://boards.straightdope.com/t/can-scientists-determine-whether-a-dna-sample-is-from-a-human-being/150263/30 "2003-01-23T19:36:22Z")
> [@](#): > > \*Originally posted by dauerbach \* > \*\*Ok, I tried to find this on the web and could not. Could I have some cites please. \*\* I gave you a cite. ---
**Author:** ![Colibri](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/colibri/32/1841_2.png) [@Colibri](https://boards.straightdope.com/u/Colibri)\ **Post date:** [January 23, 2003, 7:48pm UTC](https://boards.straightdope.com/t/can-scientists-determine-whether-a-dna-sample-is-from-a-human-being/150263/31 "2003-01-23T19:48:35Z")
But if you insist: [http://www.tepnel.com/news\_archive/050602\_biokits.asp](http://www.tepnel.com/news_archive/050602_biokits.asp) [http://www.dna-surveillance.auckland.ac.nz/](http://www.dna-surveillance.auckland.ac.nz/) [http://ift.confex.com/ift/2002/techprogram/paper\_13620.htm](http://ift.confex.com/ift/2002/techprogram/paper_13620.htm) [http://www.sciencenews.org/sn\_arc98/8\_22\_98/fob1.htm](http://www.sciencenews.org/sn_arc98/8_22_98/fob1.htm) [http://na.nefsc.noaa.gov/sharks/coop/novadna.html](http://na.nefsc.noaa.gov/sharks/coop/novadna.html) [http://rev.tamu.edu/stories/02/011502-4.html](http://rev.tamu.edu/stories/02/011502-4.html) [http://www.poultryscience.org/psa/toc/papers/01/ps01522.pdf](http://www.poultryscience.org/psa/toc/papers/01/ps01522.pdf) [http://herb.bio.nau.edu/~genetics/abstract/blackett.htm](http://herb.bio.nau.edu/~genetics/abstract/blackett.htm) [http://www.forensicdna.ca/](http://www.forensicdna.ca/) There are about 200,000 other links out there ---
**Author:** ![dauerbach](https://avatars.discourse-cdn.com/v4/letter/d/c2a13f/32.png) [@dauerbach](https://boards.straightdope.com/u/dauerbach)\ **Post date:** [January 23, 2003, 7:59pm UTC](https://boards.straightdope.com/t/can-scientists-determine-whether-a-dna-sample-is-from-a-human-being/150263/32 "2003-01-23T19:59:57Z")
Thank you colibri. Finally, and at last I am satified and admit I am wrong. [Previous page](https://boards.straightdope.com/t/can-scientists-determine-whether-a-dna-sample-is-from-a-human-being/150263.md?page=1)