Science of Admixture

Garrett Hellenthal, statistical geneticist at the Genetic Institute, University College London, gave a very interesting talk at the recent Who Do You Think You Are convention in England on the science of how DNA companies predict ethnicity. Given that ethnicity is the main reason why the majority of clients get their DNA tested at AncestryDNA, it is a very good overview of just how the different DNA testing companies arrive at their ethnicity conclusions.

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Gedmatch and WikiTree

Gedmatch is now accepting links to WikiTree, which shows up in the new Ged/Wiki column. This is a welcome alternative to uploading a gedcom, which needs to be deleted and reuploaded each time changes are made to the gedcom, because it allows the tree to be continuously updated in the WikiTree community and always the latest version will be available in the link. To learn more about this new feature click here.

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Match Maker Breaker

A new tool for phasing created by Philip Gammon called Match Maker Breaker. Roberta Estes has written up a description on how to use the tool. This is an advanced tool for helping to eliminate false matches that are IBS. It requires a fresh cuppa and a quiet zone to concentrate

Introducing the Match Maker Breaker tool for phasing

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Australian donor conceived

Medical research scientist and donor conceived Damian Adams

There was an interesting interview on ABC Nightlife about the ethical and scientific position of Australians who are donor conceived. You can listen to the interview with medical scientist Damian Adams and Associate Professor in Health Law, Dr Sonja Allen.

The legal and ethical complexities of sperm and egg donation

You can also read an article featuring Damian Adams and the issues surrounding donor conception here:
Q&A Damian Adams

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Gedmatch Generations

One of the tools on Gedmatch that is very useful but which causes some confusion is the column headed “Gen”, which means “Generations”. The number in this column means the estimated number of generations back to the common ancestor shared by you and your match. Whilst we easily understand that 2 generations back to a common ancestor means we are cousins, 3 generations back means we are second cousins and so on, but what confuses many people is how can you have in-between numbers like 2.6, 3.9, 4.1?

This number is to be understood as a guestimate or guideline that shows roughly how far back you might start looking for your common ancestor. To quote genealogist Kerry Scott, the generation estimates are “not etched in stone – they are etched in sand at best!” This is due to the random way that DNA is inherited between each generation – it is very common, once you get beyond a couple of generations, for a segment of DNA to remain intact and be passed down over several generations without changing. This means that the number of generations given with your match might also be exactly the same as that shown with your match’s parent or grandparent!

Another problem comes when you might be three generations back to a common ancestor and your match is from a closer generation and they are only two generations back to the same common ancestor. How do you work that out?!

So I had a look at the known connections I have with my genetic cousins who’ve uploaded to Gedmatch and this is the range of how Gedmatch calculated the generation distance to the most recent common ancestors and then I give the actual relationships. As you can see, the further distant the common ancestor, the more varied are the possible relationships.

Gen 1
Well, that’s easy – it’s always going to be a parent-child relationship

Gen 1.2
Oddly, this is always a sibling relationship

Gen 1.4
Uncle ~ niece

Gen 1.5
Uncle ~ niece
This makes sense: the common ancestors for my uncle are his parents, which is 1 generation, but for me, his niece, it is my grandparents, 2 generations. Therefore, the Gedmatch Generation is calculated as being between 1 and 2 = 1.5

Gen 1.6
Uncle/aunt ~ niece/nephew

Gen 1.9
1C (first cousins), whose common ancestors are their grandparents, which is 2 generations

Gen 2.2
1C (first cousins)
1C1R (first cousins once removed)

Gen 2.3
1C1R (first cousins once removed)

Gen 2.5
1C1R (first cousins once removed)
Again, this makes sense: my cousin is a generation older than me, his grandparents, which is 2 generations, are my great-grandparents, which is 3 generations. Therefore, the Gedmatch Generation is calculated as being between 2 and 3 = 2.5

Gen 2.6
1C1R (first cousins once removed)
2C (second cousins)

Gen 2.9
2C (second cousins)

Gen 3.0
2C (second cousins)
This is the ideal scenario, with the common shared ancestors for me and my match both being 3 generations back.

Gen 3.3
2C1R (second cousins once removed)

Gen 3.5
2C1R (second cousins once removed)
Again, this makes sense: my second cousin is a generation older than me, her G-grandparents, which is 3 generations, are my GG-grandparents, which is 4 generations.Therefore, the Gedmatch Generation is calculated as being between 3 and 4 = 3.5
3C (third cousins)
2C2R (second cousins twice removed)
Here we have a case of our common ancestors being my G-grandparents, 3 generations, but these ancestors are my matches GGG-grandparents, 5 generations: a difference of two generations between me and my match

Gen 3.6
2C1R (second cousins once removed)
3C (third cousins)

Gen 3.7
2C1R (second cousins once removed)
3C (third cousins)
3C1R (third cousins once removed)

Gen 3.8
2C2R (second cousins twice removed)
3C (third cousins)

Gen 3.9
3C1R (third cousins once removed)

Gen 4.0
3C (third cousins)
This is the ideal scenario, with the common shared ancestors for me and my match both being 4 generations back.

Gen 4.1
2C1R (second cousins once removed)
2C2R (second cousins twice removed)
2C3R (second cousins three times removed)
This is quite an unusual because our shared common ancestors are my GGGG-grandparents, 6 generations back, but my match’s shared common ancestors are only his G-grandparents. That’s a difference of three generations, even though my match is just 10 years older than me! This is because I am descended from the eldest child of our common ancestor, but my match is descended from the youngest child, who was 25 years younger; and likewise my ancestors were the eldest of young parents, but my cousin’s parents and grandparents had children late in life, which resulted in this apparent shift of three generations even though me and my match are in the same present-day generation! Yes, just think about it for a moment 😀
3C1R (third cousins once removed)

Gen 4.2
2C1R (second cousins once removed)

Gen 4.3
3C (third cousins)

Gen 4.4
2C2R (second cousins twice removed)
3C (third cousins)
3C1R (third cousins once removed)
3C2R (third cousins twice removed)
4C (fourth cousins)
4C1R (fourth cousins once removed)

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Y-DNA and Ned Kelly

Ned Kelly the day before he was hanged, 10 Nov 1880

Whether you regard Ned Kelly as a folk hero or just a murderous criminal, the ongoing search for which of the Irish Kelly clans he belonged to is an interesting Y-DNA story. Because neither Ned nor his two brothers had any children, there is a move to exhume the remains of their father John “Red” Kelly in order to analyse his Y-DNA. This action has been suggested by the international Kelly one-name study group, administered from Ireland.

To read more about this interesting use of Y-DNA, see the article in the Herald Sun:
A quest is underway to discover the missing link to bushranger Ned Kelly’s bloodline

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Aboriginal Heritage Project

Prof Cooper and his team at the Australian Centre for Ancient DNA have just published a new article in Nature about the Aboriginal Heritage Project which sheds light on the deep history of Aboriginal migration over 50,000 years ago.

Here are the links:
Nature article: Aboriginal mitogenomes reveal 50,000 years of regionalism in Australia
ABC Science News: DNA confirms Aboriginal people have a long-lasting connection to country

Here is a video about the Aboriginal Heritage Project from the Adelaide University

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