{"id":2841,"date":"2022-11-20T15:23:16","date_gmt":"2022-11-20T15:23:16","guid":{"rendered":"https:\/\/saturdaydna.com\/2022\/11\/mapowanie-chromosomow-w-sluzbie-genealogii-po-kim-mam-ten-fragment-dna\/"},"modified":"2023-03-05T17:17:29","modified_gmt":"2023-03-05T17:17:29","slug":"mapowanie-chromosomow-w-sluzbie-genealogii-po-kim-mam-ten-fragment-dna","status":"publish","type":"post","link":"https:\/\/saturdaydna.com\/en\/2022\/11\/mapowanie-chromosomow-w-sluzbie-genealogii-po-kim-mam-ten-fragment-dna\/","title":{"rendered":"Who do I got this DNA piece from? Chromosome mapping in genealogy"},"content":{"rendered":"\n

Below you will find an article prepared for 9. Geneami Genealogical Conference (2022) as well as the recording from a Q&A session that took place a few days after the conference. <\/p>\n\n\n\n\n\n\n\n

I got the DNA test results. What now?\u00a0<\/h2>\n\n\n\n

When we’re anxiously awaiting the results of our genealogical DNA test we often hope, that the relatives we will meet are also going to be passionate about genealogy, with beautiful genealogical trees already prepared, and that it will make it easier for us to find shared ancestors. <\/p>\n\n\n\n

However, the truth is that many people don’t have a genealogical tree or they only have information on their parents and grandparents. <\/p>\n\n\n\n

\ud83e\uddec How to find out, what degree of kinship we have if we share DNA but the relative has no information on their genealogy?<\/p>\n\n\n\n

\ud83e\uddec Can I see, in which chromosomes I have DNA from my great great grandparents? <\/p>\n\n\n\n

\ud83e\uddec Did my grandma also have the gen for curly hair? <\/p>\n\n\n\n

\ud83e\uddec Who did I get my eye colour after? <\/p>\n\n\n\n

To find answers to these and similar questions we will use chromosome mapping – a technique making genealogical research easier. <\/p>\n\n\n\n

If we have a chromosome map, we can look at segments of our DNA that we share with a relative and we will be able to tell, who our shared ancestors were, even if this relative has no genealogical tree developed!<\/p>\n\n\n\n

Sounds interesting? Let’s create a map!<\/p>\n\n\n\n

<\/p>\n\n\n\n

Mini dictionary of genetic genealogy terms<\/h2>\n\n\n\n

At the beginning let’s remember the terms, that will be used later in the article. They are useful to get to know the basics of genetic genealogy and will help us understand the chromosome mapping method. <\/p>\n\n\n\n

Centimorgan (cM)<\/strong> \u2013 Measuring unit for shared DNS <\/span>2<\/sup><\/a><\/span> <\/p>\n\n\n\n

We can think of centimorgans in the same way. The rule is that the more centimorgans we share with someone, the closer we are related to that person. For example, we share around 3500 cM with each of our parents, around 1750 cM with each grandma\/grandpa, and with a second-degree cousin (shared great grandparents) around 230 cM.<\/p>\n\n\n\n

<\/p>\n\n\n\n

Match<\/strong> \u2013 a relative, with whom we share DNA. <\/p>\n\n\n\n

Autosomal chromosomes<\/strong> \u2013 22 pairs of chromosomes ie. 44 autosomal chromosomes. They contain information about around 6-8 generations of ancestors. Their numbering is according to side (no.1 is the biggest, no. 22 the smallest). For our chromosome map we will get data from autosomal tests: 23andMe, Ancestry, Family Tree DNA <\/span>3<\/sup><\/a><\/span>, My Heritage.<\/p>\n\n\n\n

Sex chromosomes<\/strong> \u2013 this is the 23rd pair of chromosomes, which are known as X and Y. Women inherit two X chromosomes, one after the mother and one after the father. Men inherit one X chromosome after the mother and after the father, they inherit a Y chromosome. This means that men don’t give their X chromosome to their sons, only to daughters. <\/p>\n\n\n\n

<\/p>\n\n\n\n

What is chromosome mapping?\u00a0<\/h2>\n\n\n\n
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Chromosome mapping is a method of assigning DNA fragments, which we share with a relative to a certain ancestor or a pair of ancestors<\/em>.<\/p>\nMarta Sobota<\/cite><\/blockquote>\n\n\n\n

The infographic below depicts a simplified genealogical diagram of Marta and Micha\u0142, who are second-degree cousins (they share great-grandparents) and share 230cM of DNA. <\/p>\n\n\n\n

So we know, that the parts of DNA that Marta and Micha\u0142 share have been inherited from great-grandparents – Antoni and Krystyna. <\/p>\n\n\n\n

<\/p>\n\n\n\n

<\/div>\n\n\n\n

On our map we can assign it to:<\/p>\n\n\n\n

    \n
  1. A pair of ancestors – Antoni and Krystyna<\/li>\n\n\n\n
  2. One ancestor, when making a map for Micha\u0142 to his grandma Danuta and in Marta’s case to her grandpa Leonard. <\/li>\n<\/ol>\n\n\n\n

    There are two systems of assigning the segments – either to a pair of ancestors or to a single ancestor. Both are correct but I’d recommend assigning to one ancestor for two reasons: <\/p>\n\n\n\n

      \n
    1. sometimes our family has lived somewhere for many generations and at the beginning, we might n\u00f3w know, that we are related to someone in two different lines. F.ex. on our mother’s side through our great grandma and on our father’s side through a great great great grandfather. <\/li>\n\n\n\n
    2. when we create a map for a person from an endogamous community, f.ex. a community of Ashkenazi Jews, where marriages of cousins happen in many generations, assigning segments to one ancestor also makes it clearer, from whom they were inherited. <\/li>\n<\/ol>\n\n\n\n

      How to create a chromosome map?<\/h2>\n\n\n\n

      A chromosome map can be created in many ways: on a piece of paper, in an Excel sheet but for beginners I would recommend the Chromosome Map tool on DNA Painter website. Many will recognize this website from The shared cM project tool, which shows us possible degrees of kinship, depending on how many centimorgans of DNA we share with someone. Creating a map on the DNA Painter website is free. <\/p>\n\n\n\n

      The first step to creating a map is registering in the service. <\/span>4<\/sup><\/a><\/span>. Next, we can start building our map in four easy steps: <\/p>\n\n\n\n

        \n
      1. Creating a new map or opening an existing one <\/li>\n\n\n\n
      2. Choosing a person and source of data \n