-A high school student from the U.K.
January 13, 2015
Double cousin is the usual term that is used. But you are also as related as half-sisters.
Instead of the usual 12.5% of DNA that first cousins share, the two of you share around 25% of your DNA. This is the same amount that you would share with a grandparent, a half sibling or an aunt or uncle.
Let’s get into a discussion of why the two of you share 25% of your DNA.
Now let’s expand things out a bit to include grandparents:
As you can see, a grandchild gets around 25% of her DNA from each grandparent. So she has ¼ dark pink, ¼ light pink, ¼ dark blue and ¼ light blue.
And her parents got 50% of their DNA from each of their parents. So mom has half light blue and half light pink and dad has half dark blue and half dark pink.
DNA is Stored as Chromosomes
The first thing we need to do is to give each person two rectangles of different colors. These are supposed to represent that our DNA is organized into chromosomes.
This is still too simple as we each have 23 pairs of chromosomes but it is a start. You can just take what we learn from the one pair I will be showing and expand it to the other 22 pairs. (Well, to be a stickler, 21 of the pairs. The X and Y pair in males acts differently.)
OK so here is what someone will look like now: