GEDmatch.com has a wonderful free tool called Are Your Parents Related which I have previously blogged about (click here). This function looks at your raw DNA results for long stretches where you have the exact same DNA on each side of a paired chromosome, known as Runs Of Homozygosity (ROH). In other words where you got the exact same DNA from each parent. I always check this for unknown parentage cases.
When you have ROH segments, it is expected that your parents are related. However there is one other way this can happen: in very rare cases, you can get a whole or partial chromosome from only one parent. This is known as uniparental disomy (UPD).
An example of UPD on chromosome 6 from the Are Your Parents Related (AYPR) tool.
How can you tell that this is the case? Likely it is UPD when you have only one ROH segment and it is for the whole chromosome like the image above or for one arm of a chromosome (from or up to the centromere). In the less than one hundred cases I have looked at, I have seen UPD only twice. Once a whole chromosome as shown above and once the long arm of chromosome 14.
UPD can result in some dangerous medical conditions as per Science Direct (click here). Please see a professional genetic councilor if you suspect you have this.
Ellis Island has wonderful displays about immigration to America going back to the land bridge; even though it itself was only used from 1892- 1924. Although it did not close until 1954, in those later years it was only used for exceptional cases, since screening was done at the other end. This came about due to the increased restrictions on immigration (see list at the end of this article), most importantly the National Origins Act of 1924. Click here for the history of Ellis Island and click here for the BBC series of articles “The Open Door policy and immigration to 1928.”
The displays at Ellis Island have photos and letters and recorded voices but what struck me the most was the fact that there were so many anti-immigrant demonstrations back in the 19th century. I learned about them from an exhibit on the 2nd floor and thus learned that that sort of sentiment is not new. First it was the Irish immigrants, then the Chinese, then the Southern Europeans, and so on. There was the No Nothing party and the Nativists in the mid 1800s (click here for an article on the Know Nothings). I don’t remember much of this from my high school American history classes. Was it even covered to the extent shown on those walls?