The SGM Plus system of DNA analysis targets ten loci, each of which contains two alleles. These are the “short tandem repeats” that vary between individuals. In addition, a further locus is targeted that acts as in indicator of the sex of the donor. A “full” DNA profile is one in which all of these loci have produced a reliable and reportable result. Occasionally, the processes used to target some of these loci fail, resulting in an incomplete or “partial” DNA profile. The most common reasons for such failure are either that a very small amount of DNA was present in the sample, the DNA may have become degraded, or that substances may have been present in the sample that may have inhibited the analysis process. Depending on the degree of success of the DNA analysis, the match probability calculated from a partial DNA profile may be reduced below the 1 in 1 billion that would be obtained from a full profile.
What we would expect to find then in this example is that the two descendants of John show a very close match, and the two descendants of James also show a very close match (because we know from conventional paper based research that they are related). If all four match very closely, then that’s further evidence to add to our theory that John and James were really brothers. Not conclusive proof- but pretty solid evidence.
23andMe started out by testing for genetic markers of diseases and medical conditions before rolling that back in response to the governmental concerns. It has since started slowly adding more health-related features with approval from the FDA. In April, 23andMe got approval to offer risk analysis for ten genetically linked diseases. The company now offers two options: Health + Ancestry ($199) and Ancestry ($99). The Health + Ancestry plan includes testing for genetic health risks and carrier status, as well as reports on your genetic weight, hair loss, and other traits.
The test kit gathers saliva from spit. It offers a free family tree tool to which users can contribute their specific results. You can also download your full DNA profile and import that data into another tool -- but it doesn't offer a chromosome browser, so you can't really do DNA segment comparisons. Given this, if you're a true DNA geek, Ancestry may not be the service for you.
The DNA tests we reviewed either require a saliva or cheek cell sample. Saliva-collecting kits include a tube that’s marked with a fill line and sample number. The tube often has a liquid-filled cap with a stabilizer that acts as a preservative to protect your DNA from degradation during transport. Cheek swab sample kits include one or two swabs for scraping the insides of your cheeks for 30 seconds to a minute to collect cheek cells and some sort of container to place the used swabs into after collection. This prevents contamination. Our testers found upsides to both types of kits but generally preferred saliva collection kits, even though they took longer.
The introduction of home DNA testing means that anyone who wants to can now order their own DNA profiling kit online, and one common reason is for DNA identification. This is often important for those who work in high risk jobs, in case there is an accident that means their body would need to be identified. For example, the US army requires all active service personnel to submit a DNA sample upon enrolment, primarily for the purpose of identification if they are killed in service. Not everyone who works in a high-risk profession is given this option by their employer, but individuals with dangerous jobs are free to buy their own DNA profile from a private testing company.
The situation is made even more complex if it is considered that three or more people may have contributed to a particular DNA result. Often, in such cases, it is not possible for a scientist to undertake a reliable statistical evaluation of the mixed DNA result. If the DNA result indicates that a very low level of DNA has been detected, it is recommended that the reporting forensic scientist consider the possibility that the result may have been derived from a very low level of DNA from more than one person, some of the components of which may be missing from the DNA result because of the low level of DNA present
Lets suppose, as we have in the Sinnott/Sennett one name study, we have a whole lot of families who all believe their common ancestor came from Co Wexford, but the paper trail for conventional genealogy research has dwindled away, or we suspect that John and James who emigrated to the US about the same time were brothers but there is no documentation to prove it – genealogical DNA studies can now be used to show whether its possible that two families (that are at the moment quite separate on paper) are actually related and have a common ancestor. And no, we don’t have to go digging up g-g-g-g-grandfather John to get his DNA – remember, he passed it on to his son, and his son’s son, and so on to the present day. So we find a living male descendant and they get their Y-DNA analysed. That gives us a pretty good indication of the genetic signature for the whole family tree (well, the male side, anyway). If we want to check it, we find a distant cousin of the first person who tested and get their DNA analysed. If its a very close match, then bingo – we know the Y-DNA genetic signature (and whats known as a haplogroup) for our whole family group.
When I found out about AncestryDNA, I thought this could be the perfect tool to pinpoint where my family emigrated over the past few hundred years (AncestryDNA can actually go back 1000 years) and give me a focus where to take my search next. When I got the email that my results were ready I felt like a kid on Christmas day. They revealed that I was only 40% British, 25% German and 35% Greek. I’ve now focused my search on these three countries and already discovered ancestors I never knew existed.
If you are interested in doing in-depth analysis, the firm offers a chromosome browser, allows raw data to be uploaded, provides support for setting different segment matching thresholds, and allows up to five comparisons to be done at once. Family Tree DNA allows trial transfers from 23andMe and AncestryDNA into its match database; additional transfers of various datasets is available for a fee. The company promises to keep data for 25 years.
AncestryDNA, 23andMe, HomeDNA, Living DNA, and MyHeritage DNA all provide reports of your ethnicity, some showing maps of where your ancestors lived along with information about the particular countries and regions. National Geographic goes further back, pinpointing where in Africa your ancestors came from and tracing migration patterns through to near-present times. It's less about your personal genetic makeup and more about who your ancestors were and how you're connected to the beginning of civilization.
I once heard someone explain DNA as being like a cake recipe book in a library. You can take the book out of the library and even unravel it by taking out the pages. You follow the cake recipes inside the book but when ever you make the cake it never turns out quite the same way twice. When you've finished you have to return the recipe book to the library because that is where its stored. Made sense to me at the time
In fairness to 23andME, it leaves it up to the customer to unlock the more serious results – or not. When I unlock mine, I discover that, while I’m not genetically predisposed to such things as the BRAC1 or BRAC2 variant, Parkinson’s or MS, I have one of the variants for late-onset (mid-80s) Alzheimer’s. However, I don’t have any other markers for Alzheimer’s or family history or conditions associated with it or anything else listed in the rather lengthy disclaimer, which also stresses that it’s not a diagnostic result and to seek further advice from your GP if you are concerned.
If you’re more interested in learning about the relatives you already know you have, 23andMe has a few unique tools that let you compare your DNA with your children, parents and grandparents. If multiple people in your family tree want to get tested, fill out a GrandTree, which shows you which segments of DNA you inherit from each of your tested parents or grandparents. While nowhere near as comprehensive as AncestryDNA’s family tree and genealogy tools, 23andMe’s more nuclear approach to family genetics is a great option that lets you explore your genetic relationship with more immediate relations.