How Often Does DNA Recombine?
Recombination is the mechanism that gives variety to our DNA. It's how segments are created. Now we've had a viewer ask us, "How often does DNA recombine?" Let's answer that for you today.
This question could be taken in a couple of different ways. The easy explanation is that DNA recombines whenever new gametes are formed. In other words, whenever sperm or eggs are formed, recombination events happen.
I think people are really asking how often our are 22 autosomal DNA chromosomes recombining?
In this video, I compared the DNA results from my cousin and myself. My father and my cousin's mother are siblings.
My DNA represents paternal grandfather recombination.
My cousin's DNA represents maternal grandfather recombinations.
We can use the following two graphics to learn a lot about how often recombination happens.
Notice the map chromosome browser for my first eight chromosomes, which comparing my grandfather and me.
Remember, the black region is Not a Match, representing the DNA from my paternal grandmother. The blue regions represent Fully Identical Regions - so I receive those segments from my paternal grandfather.
Wherever the black regions change to blue, that indicates a recombination point.
Above, you can see the chromosome comparison between my cousin and our most recent common ancestor - our grandfather. However, my grandfather to him is that of a maternal grandfather. Understanding the difference is important for later in this blog post.
While comparing both chromosomes browsers, it looks like he has some more recombination points than I do. Since we're first cousins, we should have approximately the same amount of black and blue segments, even though they are distributed differently.
How Many Recombination Points Do We Have?
When I count the number of recombination points on my first eight chromosomes, I have 9 paternal recombination points.
Meanwhile, my cousin had 29 maternal recombination points.
My cousin has three times the number of recombination points that I have.
How often does maternal DNA recombine more than paternal DNA?
When you look at the total recombination difference between my cousin and me, you might wonder, "How common is this?"
There have been several recombination studies that have been done, including the following:
All of these come up with the same answer. Basically, maternal recombination happens more often than paternal recombination.
You can see it on this graph here, the ranges and percentages of times amounts of certain recombination happen.
In males, typically, it's about 20 - 23 recombinations.
In females, it is typically around 38 - 45 recombinations.
So there's actually a significant difference in that number. There's a little bit of overlap right around the 30 range, but not much.
So if you are looking at your DNA with your grandparents. It depends on if it is a paternal grandfather or a maternal grandfather. What you will see is that if it's a paternal grandfather, you're gonna have fewer recombination points. But if you're looking at a maternal grandfather, it's going to be more.
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