Recently I was asked whether there is a way to tell a full sibling from a half sibling. Sometimes the total centimorgans are low for one but high for the other. You expect to share about 2550 cM with a full sibling and 1700 with a half sibling; so which is it if you share 2100 cM?
The answer is that full siblings will share many fully identical regions (FIRs), over about 25% of their chromosomes. Half siblings will have no FIRs of any significant size. The exception being some small ones if their parents are from the same population group but still far far fewer than a full sibling.
Here is a comparison of my first eight chromosomes with my brother made at GEDmatch. The green bars are where we are fully identical, in other words we got the same segment of DNA from each of our parents there.
GEDmatch comparison of me and my brother (full siblings)
You can click on the image to see the entire display at GEDmatch that this was made from.
National DNA day on April 25 celebrates the day that Crick, Watson, et al published their papers on the structure of DNA. There is an article in Wikipedia about it at https://en.wikipedia.org/wiki/DNA_Day
Both Ancestry.com and Family Tree DNA have been celebrating this date with sales of autosomal DNA test kits that end today. So buy a few!
23andme did not have a sale, but has sent a $50 off coupon out to people who have already tested there as a mother’s day sale or gift and that is good through next Sunday.
See my DNA testing page for a comparison of the sites. Remember that if you test at ancestry you can transfer those results to Family Tree DNA (click here for my post on that with the details)
Discovering where your ancestors came from is one of the more popular reasons to do a DNA test but the current ancestry composition algorithms have a long way to go. Sometimes East Asian ancestry is actually American Indian and South Asian might be gypsy or Indian Indian. Scandinavian might be British or North German and British and Irish might be Scandinavian.
Most efforts to analyze the deeper roots of your ancestry are based on samples of modern populations who self report four grandparents of a single ethnicity plus some public databases and a few ancient samples. Since each company relies greatly on their own databases of tested people, it is not surprising to see differences in their predictions.
My brother’s Ancestry as shown at DNA.land
Since my brother is tested at all three companies I thought I would post the images of what each company sees in his DNA as well show the new report from DNA.land and a few from GEDmatch (both using his uploaded Ancestry.com DNA data). We are confident of our recent ancestry: 50% Southern Norwegian, 25% Bavarian German and 25% Ashkenazi.
The new DNA.land report is shown above, Hmmm, only 16% Ashkenazi.
A week ago on Easter Sunday my 96 year old Dad died. He was ready, but I was not. He had a wonderful life and everyone in his assisted living facility adored him. I was told he was a real gentleman, he was sweet, he sang so beautifully … When mother died seven years ago, we did not expect Dad to last long after her. They were married for 62 years and were still very much in love.
But that Norwegian optimism kept him going. Some days he thought I was my mother, some days he thought I was his mother, but after about a year he was back to his charming self and usually knew I was his daughter. This is one of my favorite pictures of them taken when I was a toddler.
Larry Munson, baby Kitty Munson, Gretchen Munson 1951
Here is his obituary:
We are taking him home to East Hampton for his final rest, service on April 22 at 11:30 St Luke’s church.