![]() In the following example, you can see that Mary, Anne and Sue all match Mom, because they all have all As. This is true whether or not you’ve been able to identify the ancestor responsible for those shared segments. Those people also match each other on the same segment.Two or more people match you on a particular segment.In fact, the definition of a proven ancestral “match” in genetic genealogy is when: This is the underlying foundation of why we use triangulation and can say that if three people with a known ancestor all match each other, we can map that segment as IBD, identical by descent, from that known ancestor. Because my matches to both Mary on my mother’s side and Myrtle on my father’s side are IBD, Joe also does NOT match Mary or Myrtle. In this case, as you can see, Joe does not match my parents. The acid test of whether I match Joe by descent (IBD) or by chance (IBS) is if Joe matches my parents. I match Joe, because I carry both A and C at each of these locations. This is the textbook case of IBD, or identical by descent.īut then, there’s Joe. In this case, I match both Mary and Myrtle, and Mary and Myrtle each match a respective parent. Ideally, if we could separate my values into Mom and Dad’s columns, like above, then we could match exactly against cousins from Mom’s side and from Dad’s side, because those cousins would also carry all As or all Cs in part or all of those locations, like in the example above. In other words, they are combined and I can’t tell the difference – at least not without either Mom or Dad’s data to compare against. My results for these locations look like this – a mixture of Mom’s and Dad’s in no order. In this example, Mom contributed all As and Dad contributed all Cs. Our autosomal DNA, when read, does not and cannot separate Mom’s contribution from Dad’s (except for the X chromosome in some situations, which we are not going to discuss in this article.) I discussed this in detail in this article. We carry two nucleotides in each inherited position, one from Mom and one from Dad. It would be very useful….very…if our DNA came in nice straight columns, with Mom’s on one side and Dad’s on the other. But first, let’s talk about why we need phasing at all.īecause there is no zipper in our DNA. A second type, which I’ll call academic phasing, has wider applications. ![]() Originally phasing was used to mean parent phasing. These are really two kinds of phasing, used for two different purposes. ![]() Today, it’s often used generally to imply that phasing would improve our matches and therefore “should be done.” As the industry has developed, phasing has taken on a slightly different meaning. The goal of phasing originally was to determine which side of our family, Mom or Dad, a piece of our DNA, and therefore a particular match, came from. Many people don’t understand what phasing is, why it’s important, and that there are really two kinds of phasing. One of the terms used in genetic genealogy is phasing. I’ve had several questions about what phasing is, why it might be important, and how phasing affects matching. Over the past few weeks there has been quite a bit of discussion surrounding phasing and matching of autosomal DNA. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |