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DNA

The Science Behind AncestryDNA — #NGS2017GEN

Chromosome inheritance diagram credit Ancestry.comJulie Granka, of AncestryDNA, spoke about “Understanding the Science Behind Your DNA Results” at the 2017 National Genealogical Society Conference last week. I’m hardly qualified to report about this session, but I’ll give it a try. Julie started by defining several terms, utilizing lots of diagrams. I was hoping to link to some pages on Ancestry.com that contain explanations as clear and simple as Julie’s. No luck. If I am going to provide links to basic information about DNA and genealogy, I will have to send you to someplace other than Ancestry. That is too bad. They should publish Julie’s presentation on their website.

Judy Russell, The Legal Genealogist, has provided a nice list of links to introductory information. See “DNA Basics for a Sound Foundation.”

Suffice it to say, there are basic building blocks of DNA that are represented by the letters A, C, G, and T. Our chromosomes are composed of long strings of these—3 billion, in fact. Almost all the letters are the same in every single person on the planet. Julie said that only about 10 million are different among different individuals and populations. A DNA test looks at about 700,000 of them. A location in the string of letters where the letters differ between individuals is called a SNP (pronounced “snip”). A group of inherited letters is called a haplotype.

Julie studies SNPs and haplotypes in the context of human populations. “Patterns of SNPs and haplotypes among human populations are driven by history,” she said. “As humans migrate, they bring their DNA with them.” She explained the founder effect: Not everyone in a population has the same SNPs and haplotypes. If a small number of people migrate somewhere, their most common SNPs and haplotypes are likely to be different than the parent population. They have founded a population with a different profile than the parent population. A related phenomena is isolation. If I understand correctly, newborns in an isolated population are statistically more likely to have the most common SNPs and haplotypes of their population. These effects make different populations look different genetically.

AncestryDNA uses the SNPs and haplotypes to determine three things. 

  • Tiny amounts of the haplotypes and SNPs associated with a population from the distant past (hundreds of thousands of years) survive in our DNA. AncestryDNA uses this information to provide your ethnicity estimates. To determine what SNPs and haplotypes are associated with distant populations, AncestryDNA uses reference panels. These are individuals whose haplotypes and SNPs are thought to be representative of the distant populations. AncestryDNA has 26 reference panels. Founder effect and isolation make ethnicity estimates easy. Migration makes ethnicity estimates difficult.
  • Large amounts of shared haplotypes between two persons indicate recent common ancestors. The more closely related, the more DNA is shared. AncestryDNA uses this information to provide your DNA matches. There are several challenges in determining DNA matches. Just sharing DNA doesn’t mean you are closely related. DNA you share for other reasons is called identical by state (IBS). DNA shared because of recent common ancestry is called identical by descent (IBD). AncestryDNA has to determine the difference. Another challenge arises from the way DNA is processed in the laboratory. For any given SNP, the data coming from the lab does not differentiate between the value contributed by your father and the value coming from your mother. AncestryDNA uses tools to estimate which came from which. She didn’t say this, but I would guess that if they ever get it wrong, you could be shown relatives who aren’t really your relatives.
  • In between the two extremes, AncestryDNA searches for groups of people who share large numbers of matches to others within a group. They use this information to provide your Genetic Communities.

It is possible to share no DNA at all with cousins. The closer the cousin, the higher the probability of shared DNA. Julie showed these numbers:

Cousin Probability of shared DNA
1st 100
2nd 100
3rd 98
4th 71
5th 32
6th 11
7th 3.2

She showed a chart that looked like the one below. I think it indicated the average amount of shared DNA between two close relatives. It went by so fast, I am not certain. However, Blaine T. Bettinger provides similar data, which I’ve charted below.

Blaine T. Bettinger, “The Shared CM Project – Version 2.0 (June 25, 2016),” PDF chart, _The Genetic Genealogist_ (http://www.thegeneticgenealogist.com : updated 31 July 2016).
Source: Blaine T. Bettinger, “The Shared CM Project – Version 2.0 (June 25, 2016),” The Genetic Genealogist (http://www.thegeneticgenealogist.com : updated 31 July 2016).

AncestryDNA uses these numbers to estimate your relationship to your DNA matches.

She covered more, but that’s about all I have time and space for here. I’m sorry that I’m not as clear as she was, but hopefully you learned something.

 

 

Chromosome inheritance diagram credit: Catherine A. Ball, et. al., “DNA Circles White Paper,” Ancestry (http://www.ancestry.com/cs/dna-help/circles/whitepaper : updated 18 November 2014), figure 2.1.

Who Do You Think You Are? Recap: Matthew Morrison

In Who Do You Think You Are?, Matthew Morrison uncovered fascinating ancestors, each with their own tales of hardship and triumph. For some time, however, roadblocks stood in the way of discovering his ancestor’s stories. Only a tight combination of historical records and DNA could unlock the secrets in Matthew’s tree. The marriage of records Read More

The post Who Do You Think You Are? Recap: Matthew Morrison appeared first on Ancestry Blog.

After Malcom X, Facebook, DNA Databases, More: Friday Afternoon ResearchBuzz, February 22, 2019

NEW RESOURCES

CAIR: CAIR Research Director Launches ‘After Malcolm Digital Archive’ with George Mason University. “The Council on American-Islamic Relations (CAIR), the nation’s largest Muslim civil rights and advocacy organization, today announced that CAIR National Director of Research and Advocacy Dr. Abbas Barzegar has launched the ‘After Malcolm Digital Archive’ with George Mason University’s Ali Vural Ak Center for Global Islamic Studies.”

TWEAKS AND UPDATES

CNET: Mark Zuckerberg to meet with UK culture chief after ‘digital gangsters’ report. “Facebook CEO Mark Zuckerberg is set to meet with UK Culture Secretary Jeremy Wright at the company’s California headquarters on Thursday afternoon. [Yesterday – TJC] The meeting comes just days after a British government report slammed Facebook and other companies for ‘considering themselves to be ahead of and beyond the law’ and accused Zuckerberg of ‘contempt’ for the UK. ”

AZCentral: Controversial DNA database bill scaled back to patient care professionals only. “A controversial bill that would have created a massive statewide database of DNA from a myriad of professionals, volunteers and even dead people has been scaled back. Sen. David Livingston, R-Peoria, the bill sponsor, has introduced an amendment to Senate Bill 1475 that would require DNA only from professionals who care for patients with intellectual disabilities in an intermediate care facility.”

USEFUL STUFF

Make Tech Easier: 5 Chrome Extensions to Speed Up Your Browsing. “Chrome is known as the fastest browser, but for some people even fastest isn’t enough. Moreover, Chrome is also a huge memory hog and may lead to a slower browsing experience on low-end devices. Thankfully, there are many Chrome extensions available that will speed things up for you exponentially.”

MakeUseOf: How to Find Videos on Facebook. “It isn’t always easy to find what you’re looking for on Facebook. Confusing menu items and poor search results hide some of the stuff worth looking at. Videos are one of the biggest victims. With that in mind, here’s how to find videos on Facebook.”

AROUND THE SEARCH AND SOCIAL MEDIA WORLD

University of Michigan: Historical Letters In U-M Zoology Museum Archive Highlight Links Between Specimen Collection, Conservation . “Clark Schmutz spent more than 100 hours last semester reading and digitally scanning hundreds of letters in the correspondence files of the University of Michigan Museum of Zoology’s mammal collections, which date back to the 1800s. The scanning project is a multiyear effort to make the museum’s correspondence files available online. For Schmutz, who graduated in December with a double major in English and ecology, evolution and biodiversity, it was also an opportunity to search for intriguing stories that illustrate the links between museum collections and conservation.”

Independent (Ireland): Rodin statue outside Nando’s among first to feature in new database. “A statue of Eve by Auguste Rodin that sits outside a Nando’s restaurant in Harlow is one of the first to be included in a new database of publicly owned sculptures in the UK. Charitable organisation Art UK is working on what they say is the largest sculpture cataloguing project ever undertaken in the UK. They endeavour to have listed an estimated 150,000 pieces online by 2020.”

Mashable: Restoration YouTube will bring you deep into an internet rabbit hole. “The restoration community is a corner of YouTube boasting thousands of subscribers and millions of views. For the most part, it breaks down into four major subdivisions: shoes, swords and knives, small machinery, and toy restoration. Surprisingly, though, while all of these items are different, most of the content creators all had similar things to say.” The art restoration is pretty terrific too. Check out Baumgartner Restoration’s YouTube channel.

SECURITY & LEGAL

ZDNet: Adobe sends out second fix for critical Reader data leak vulnerability. “Adobe has released a second patch to resolve a critical zero-day vulnerability in Adobe Reader after its original fix failed. The vulnerability, CVE-2019-7089, was patched in Adobe’s February 12 patch release. Buried among 42 other critical bugs, the security flaw was described as a sensitive data leak problem which can lead to information disclosure when exploited.”

RESEARCH & OPINION

NewsCentral24x7: How a Script-Agnostic Media Can Empower The Illiterate. “In such an English-dominating virtual world, where technology, too, is largely developed and designed by native English-speaking persons, how do the oral or illiterate communities become a part? There is no denying that with the help of basic digital tools, people can be empowered to tell their own stories, beating long-set information exchange criterion of being able to read and write one or more script. By using the medium of spoken words and audio-visual story-telling, masses are better placed in the current information economy.” Good afternoon, Internet…

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