›Introduction to DNA and Genealogy
  ››mtDNA and Y-DNA
 ›Meiosis and Crossover


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I am creating a Gallery of Genome comparisons, so we can all learn more about the natural variation in "crossover" events which occur during meiosis, and how this affects the variation in the amount of DNA that different types of cousins share.

I am especially interested in Grandparent/Grand"child" comparisons, and sibling comparisons.

The Grandparent/Grandchild gallery can be seen here

The Sibling Gallery can be seen here



If you have grandparents/grandchildren, or siblings, or cousins that have tested with 23andMe, the genome comparison function will show what stretches of DNA you share.

What i would like are the genome comparison diagrams of people of previously known relationships

eg - Grandparent/Grand"child"

Brothers & Sisters


Uncle or Aunt/Niece or Nephew

The more diagrams that can be added, the more we will all learn by seeing the natural variation in the actual amounts of shared DNA between people of different types of relationship (compared to the theoretical average).

What do I need?

For each comparison pair:

1) The genome comparison diagram, (this is what goes in the gallery). 
   Instructions on how to get these are **here**

2) The comparison data table (this lets us know exactly where crossover occurred - the "hard" data).
   Instructions on how to get these are **here**

3) E-mail the above to me at:

4) If you have multiple related people, from multiple generations whom have tested with 23andMe (full or ancestry edition) or whom have tested with FTDNA (Family finder), then it might be helpful to also send me a diagram and/or descendantcy list and/or genealogy website link showing the relationships between the different people tested.

This is primarily to help prevent me from getting too confused, and so that I can keep track in my mind how different people are related. I don't intend on displaying any of the descendancy diagrams/charts.
Full privacy is preserved.
If you only have one or two genome comparisons then it's not really necessary (Since the fewer people you have comparisons for, the less likely it is that I will get confused by questions in my mind like: are the two grandsons of the grandmother, cousins or brothers,.. and are they full cousins/brothers or half cousins/brothers).

For example:
In the (fictional) example below, the people tested are shaded and numbered.


For Grandparent/Grandchild comparisons we have: Person 1 X Person 5
Person 1 X Person 6
Person 1 X Person 7
Person 1 X Person 8
For the Sibling comparisons we have: Person 3 X Person 4
Person 6 X Person 7
Person 6 X Person 8
Person 7 X Person 8
We also have First Cousin comparisons:
(a gallery for these will be added in a month or so)
Person 5 X Person 6
Person 5 X Person 7
Person 5 X Person 8
We also have Aunt/Uncle V's Nephew/Niece Comparisons:
(a gallery for these will be added in a month or so)

Person 2 X Person 6
Person 2 X Person 7
Person 2 X Person 8
Person 3 X Person 5
Person 4 X Person5
Person 4 X Person6
Person 4 X Person7
Person 4 X Person8

There also are several Parent/Child comparisons - but these should all be 100% half identical...


How to get the Genome comparison diagram

If the two people tested at 23andMe...
see directly below:
If the two people tested with FTDNA's "Family Finder"...
see directly below:
Click on "Family Inheritance" in the side menu, and then select the first person for comparison in the first selection box, and then select the second person for comparison in the second selection box. Log into the FTDNA account of one of the people being compared. Click on "Chromosome Browser"in the side menu, and then in the matches list, select the second person for comparison. In the "compare genes" selection box, select "1+ cM".
Position the web page to center the genome diagram, basically you want your screen view to show all of the area marked by a square in the diagrams below:

Step one - Capture your screenshot

If you have a Windows computer, you can copy your screenshot (ie what you can see on the screen) to your computer "clipboard" by pressing the "PrtScn" key (it's usually at the top right of the keyboard). If you press the "Alt" key at the same time, then just the contents of your web browser window will be copied (rather than your whole screen).

If you have a Mac computer, to copy your screenshot to your computer "clipboard" by pressing 4 specific keys at the same time. These keys are "Control" "Command" "Shift" and "3" ( Control-Command-Shift-3 ). If you instead want to directly save the screenshot as a file, you can press Command-Shift-3. This will save as a .pdf file if you have Mac OS X 10.2 or greater(if your mac OS is an earlier version, it will save as a .tiff file).

Step two - Paste the screenshot into the photo/image editing application of your choice.
(if you are using a Mac computer, and created a screenshot file instead of copying to the "Clipboard", you can miss this next step)

If you are using a program like "Paint" (which is installed along with the windows OS), First open up the program, and when it is loaded, press Ctrl and "V" at the same time (Ctrl-V).

If you are using a program like "Photoshop", first open up the program, and when it has loaded select "New" from the "File" menu. This opens a dialog box where you can define the "canvas" size. If you screen shot is already copied to the clipboard, usually the dialog box will have a preset size that matches the size of your screenshot. Click "Ok" and then select "paste" from the edit menu.

Step three - Save your file.

If you are unsure how to crop in your image editing software, just save the whole screenshot and I will crop it for you. Before I add the diagram to the comparison gallery I will crop away all names . Names will be replaced by non identifying reference numbers (eg. Child 52; Sibling 3, family 2)(I only want them in the copy you send to me, so I can keep track of who has sent me what,.. so really it's just to stop me from getting too confused)

If my instructions for how to obtain a screen shot of your Genome comparison diagram don't work, you might also like to look at the instructions at the following websites:

How to get the comparison data table

Why do I need the data table as well as the diagram?,.. because I need to standardise the results between FTDNA and 23andMe, and standardise comparisons made between people of different genders.
The reported amount of DNA shared from 23andMe includes the X chromosome (females have two and males have one), but FTDNA only reports the amount shared on the autosomal chromosomes. Because 23andMe includes the X chromosome, it is more difficult to make direct comparisons of % DNA shared between individuals of the opposite gender. More direct comparisons can be made when considering % shared autosomal DNA only.
The data table allows me to subtract the amount shared on the X-chromosome, and it also gives more precise information on the amounts shared. It is still useful to have figures on the amount shared on the X-chromosome, but because of its more complicated inheritance pattern, figures on % shared are best made seperately from Autosomal chromosome sharing.

Click on "Ancestry Labs" in the left menu, and then click on "Family inheritance:Advanced" Look for the menu on the bottom right of the FTDNA chromosome browser
You should now see a screen like the one below:
Now click on "Download table" or "Download to Excel".
When you click on "Download table" this will give you the option of either saving or opening the file. I would suggest opening it and then saving it with a suitable file name.
If you are sending me multiple comparisons, you can send all the data tables to me in a single file (with, for example, the different comparisons in different excel sheets)

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This work is licenced under a Creative Commons Licence.