Although I have found genetic genealogy to be interesting and enriching I use a much different approach with the use of DNA testing than with standard and traditional genealogy, using paper and digital image documentation. Genetic genealogy, using the science and technology behind DNA collection and analysis, looks at deep ancestry over tens of thousands, sometimes millions or billions of years, while standard and traditional genealogy looks at ancestry over generations of people, over hundreds of years, sometimes several hundred years, and even, in some rare cases, sometimes thousands of years.My experience with genealogy, family history, and genetic genealogy, is, at best, at a practiced novice level. I learned enough about DNA science as an Anthropology undergrad at Ohio State to understand the basics pretty well, even if that time in my life is coming up on a twenty year anniversary. I’ve learned how to do genealogy with the help of friends and patient and kind people who are willing to offer their wisdom and tips, and I’ve supplemented that with books, online guides, videos, and have learned the most just by doing. So, I know a thing or two, and I know I don’t know everything, but I know enough to know that I can stand to learn quite a bit more, and I embrace the feeling that I still have much to learn.
So, on that note, I’ve recently made quite a few new friends in the genealogy world who have found me one way or another to be connected to them through genetics. We have all come to find that we are genetically related, because we have found that we share similarities in our DNA. The companies we have paid to test our DNA and to provide services that will help us use the genetic information in ways that can help our genealogical pursuits have provided matching services to us that have connected us, almost like the “People you may know” type of features on Facebook and Google+ and Twitter. These DNA testing services, like the social media apps I mentioned, match us up with people based on similarities in our DNA profiles, rather than the “friends” or “followers” we have in common.
How do DNA testing companies know when two individuals share similarities in their genetics? They look for particular and distinctive, identifying mutations. They look for SNPs. “Snips”, as they are pronounced, are variations, differences in a single base pair in a DNA sequence, which are, essentially copying errors. “SNP” is an acronym for “Single Nucleotide Polymorphism”. When an existing cell divides in two to make new cells, it first copies its DNA so that the newly created cells will each have a complete set of genetic instructions. During this DNA copying process there will, inevitably, appear copying errors, mistakes. Mutations are copying errors, and these copying errors lead to variations in the DNA sequence at particular locations.
SNPs can generate biological variation between people by causing differences in the coding instructions for proteins that are written in the human genetic sequence. These differences are what can influence a variety of human traits, including hair color or susceptibility to certain diseases, possibly even a predilection towards some particular type of behavior or food preference. Where the mystery lies is in while some SNPs lead to differences in a person’s health or looks, most often they seem not to lead to any observable differences between people whatsoever.
Human DNA sequences have changed over time because of SNPs, mutations, mistakes, copying errors. These ‘errors’ are exactly what causes human variation, which, according to Charles Darwin’s great theory, has allowed humans to ‘evolve’ and to survive over time, generation after generation. DNA is passed from parent to child, so the child inherits her collection of SNPs from her parents. She will be a match with her brothers, sisters, cousins, aunts, uncles, grandmothers, and grandfathers at many of these SNPs, but she will have far fewer matches with people to whom she is only distantly related. The number of SNPs where she matches with another person can, in this way, be used to tell how closely related she and the other person are related.
DNA can be broken down into a single building block, called a nucleotide.
There are four nucleotides that I am aware of: adenine (A), guanine (G), cytosine (C), and thymine (T). When nucleotides are combined together they form DNA, which forms our genetic code, our makeup of genes. Genes build proteins, and proteins do most of the work that our bodies, and the cells that make up our bodies, do. While some proteins give cells their shape and structure, others help cells carry out biological processes like digestion or respiration. Using different combinations of nucleotides, DNA uses these building blocks to create the different proteins.
When the cell divides and the DNA is being copied, it is common that somewhere down the line there will be a mistake made in the process. One nucleotide is mis-transcribed for another. Again, this copying error is called a SNP. To give an example of how this occurs, a SNP might be the replacement of the nucleotide cytosine (C) with the nucleotide thymine (T) in a certain stretch of DNA.
According to some counts, SNPs occur, on average, once every 300 nucleotides copied. If this is correct it means that there are roughly 10 million SNPs in the human genome. In their most common form, SNPs are found in the DNA combinations that are in between our genes, and for this reason they can act as biological “markers”. Genetic markers help scientists locate genes that are associated with disease. When SNPs occur within a gene or in a regulatory region that sits near a gene, they may play a more direct role in disease by affecting the function of the gene.
So why is this important now? Stay tuned. There is exciting news to share in the next day or so.