Good morning all,
In lab this past week, we considered some of the aspects of personalized genetic testing, including the ability to estimate one's genetic heritage and family history through evaluation of genetic dissimilarities to others. Fresh on the heels of that discussion is another news report of more decades-old crimes being solved by similar kinds of genetic comparisons.
When a person offers their genetic information to 23andMe, Ancestry.com, or other of the genetic history services, their DNA sequence and its identified markers are entered into massive databases. It is only against these databases that useful comparisons can be made - we can't learn much about our genetic history by comparing our DNA to that of one or two others.
Remember that these DNA sequences can be compared for similarities and dissimilarities, and they also can be clustered into haplotypes - groups that share some common ancestry. Haplotypes are the basis for construction of genetic pedigrees, or genetic 'family trees'.
How can we solve crimes using this information? Imagine that 5 or 10% of the population of a city have their DNA stored in one of these databases. If a crime (new or old) is committed, investigators can
1) collect DNA evidence from a crime scene (easy to do, as we leave hair and cells everywhere we go)
2) compare the DNA from the crime scene to that of the collected database
3) Evaluate whether there is a direct DNA match to someone in the database. If so, that person may be the culprit! Well, if only 10% of a population has been genetically profiled, the odds of that are low. It's also likely that that people who commit crimes are not likely to freely offer their DNA to public databases.
4) But, we all have relatives. Investigators can often find similarities between the DNA collected at a crime scene, and the DNA of some family group within a database. Then, they look at the personal and family backgrounds of just those individuals. Are any of those people in the DNA database related to someone who has committed other crimes, and has a criminal history already in the police records?
This represents a very powerful way to quickly sort through a lot of information. One the one hand is a large database of genetic information. On the other hand is a large database of police records of crimes and criminals. Finding out specifically where they intersect is the key, and such a comparison often produces leads to a small number of individuals as suspects.
5) Suspects can then be watched/followed, and their DNA then sampled (for example, by collecting from the trash a drinking cup they had used). If this new DNA sample matches that collected at the crime scene, the crime may be solved.
It is exactly these methods which are being used in many cases, both new and old. Notice that they rely very heavily on personal genetic data, and, importantly, notice that suspects can be identified even if they don't offer their own DNA, as long as someone related to them already has. This is a challenge for the courts, too - what is an individual's right to privacy and protection from suspicion when your relatives implicate you, just by being related?
It's exciting to think of the possibilities for learning about one's self through DNA. It's equally important to remember that these are discoveries that we cannot make on our own - we are relying upon public and commercial databases, that can be used in ways we may not have intended or not even thought about. Science is about progress - new ideas, information, and abilities. Even as we reap the benefits of these advances, it is important that, as a society, we stay abreast of the social and ethical challenges that come with them.
Have a great weekend -