Many genetic genealogists, myself included, often talk about DNA segments getting “broken up” or “broken down” as they are passed from one generation to the next. But this language can be misleading, since DNA isn’t really “broken up” into pieces when it passed down; instead, a few pieces are traded between nonsister chromosomes in a process called RECOMBINATION.
Genetic recombination is a process of crossover between chromosomes during MEIOSIS (meiosis = a very specialized cell division that creates eggs and sperm for reproduction). Very early in meiosis, the cells duplicate the chromosomes. Normally, every cell has 23 pairs of chromosomes, for a total of 46 chromosomes. However, in the first step of meiosis, the chromosomes are duplicated to result in a total of 92 chromosomes. There are 4 copies of chromosome 1 (2 copies of the chromosome you got from your mother, and 2 copies of the chromosome you got from your father). There are 4 copies of chromosome 2, and so on.
There will be lots more to come, including guidelines for Y-DNA and mtDNA testing and interpretation, as well as some guidance for citing DNA test results in reports, scholarship, and in general. Stay Tuned!
Inspired by other end-of-year posts by Denise Levenick, Judy Russell,Roberta Estes, and others, here are my Top Five Posts in 2014. This year was a turning point for genetic genealogy as it finally switched from a cottage industry to a widely accepted commercial enterprise. I can only imagine what 2015 will bring.
Here are the top 5 visited posts, ranked from highest to lowest:
In my last post (see “Recreating a Grandmother’s Genome – Part 1”), I introduced my grandmother Jane, who died when I was just 8 years old. Although I have only a few memories of my grandmother, I have 25% of her DNA. To explore this rich genetic legacy, I’m trying to recreate as much of my grandmother’s genome as possible using the GEDmatch Tier 1 tool called “Lazarus.”
In the last post we also learned about the new Lazarus tool. In today’s post, we’ll choose what kits to use for my grandmother’s Lazarus kit.
Finding DNA Kits for Lazarus
GROUP 1 – DESCENDANTS ONLY
So GROUP 1 must be descendants of the target Lazarus kit. My grandmother has six children, twelve grandchildren, and eleven great-granchildren. Any of these 29 people are candidates for GROUP 1. Of those 29 people, I’ve tested four of the six children and one of the grandchildren (myself). Yeah, I know, I have more testing to do!
My grandmother Jane died in 1984 when I was just 8 years old. I have some really great memories of her, faded with time but still filled with emotion. Bath times, spending time with her in the summer, newspaper hats, chrysanthemums.
However, in addition to those memories, she gave me a very unique genetic heritage. She was from a region of the world with a high degree of admixture, and thus it is from her that I obtained my Native American mtDNA, my Native American, African American, and Spanish autosomal DNA. It is an incredibly rich and fascinating genetic legacy.
In an attempt to learn more about my grandmother’s genetic heritage, I’m using GEDmatch’s new Lazarus tool to try to recreate as much of her genome as possible. Join me on the journey, and learn about this new tool.
Last week I published “Small Matching Segments – Friend or Foe?” to join in the community’s conversation about the use of “small” segments of DNA, referring to segments 5 cM and smaller (although keep in mind that the term “small,” without a more specific definition, will mean different things to different people).
The question that the community has been struggling with is whether small segments of DNA can be used as genealogical evidence, and if so, how they can be used.
As I wrote in my post, a significant percentage of small segments are false positives, with the number at least 33% and likely much higher. In my examination and in the Durand paper I discuss, a false positive is defined as a small segment that is not shared between a child and at least one of the parents.
There has been a great deal of conversation in the genetic genealogy community over the past couple of weeks about the use of “small” segments of matching DNA. Typically, the term “small” refers to segments of 5 cM and smaller, although some people include segments of 7 cM or even 10 cM and smaller in the definition.
The question, essentially, is whether small segments of DNA can be used as genealogical evidence, and if so, how they can be used.
While it may seem at first that all shared segments of DNA could constitute genealogical evidence, unfortunately some small segments are IBS, creating “false positive” matches for reasons other than recent ancestry. These segments sometimes match because of lack of phasing, phasing errors, or a variety of other reasons. One thing, however, is clear: there is no debate in the genetic genealogy community that many small segments are false positive matches. There IS debate, however, regarding the rate of false positive matches, and what that means for the use of small segments as genealogical evidence.
I am incredibly honored to announce my election to the Board of Trustees of the New York Genealogical & Biographical Society! The NYG&B is the largest and oldest genealogical society in New York State, and the second oldest genealogical society in the nation. As a lifelong genealogist with New York roots dating back almost 250 years, joining the NYG&B is a dream come true for me.
Over the past decade, DNA has become a powerful tool for genealogical research. As a member of the NYG&B’s Board of Trustees, I hope to be able to help bridge the (ever-closing) gap between traditional genealogy and genetic genealogy, and help both members and non-members understand and incorporate DNA into their family histories.
The board represents an incredible group of people dedicated to helping people discovery their family histories, and I am so grateful to be able to join them. The full list is below.
Yesterday, when I checked my AncestryDNA account I had 205 pages of matches, or 10,250 matches in the database. Today, thanks to Ancestry’s new matching algorithm, I have 57 pages of matches, or 2,850 matches in the database (a reduction of 72.2%!). I also have DNA Circles, groups of people who MIGHT share a common ancestor (some of whom share DNA with me).