Genetic Genealogy and Telephone Tag
With thanks to the Sprague Genealogy Project for permission to reproduce
Have you ever played Phone Tag or Telephone Tag as a kid? Remember? It's the game you play in a circle. One person whispers a message into their neighbor's ear. Each person in turn has to repeat the "same" story to their neighbor, one by one, until it gets back to the person that originated the message.
The fun in the game is two-fold. Try not to change the original message and to laugh hysterically at the resulting message after it has passed through the group. I remember some crazy stories can come out of this game!
DNA or Y-DNA testing for genealogy is very similar to this simple example. How is that?
Let us create an example of Phone Tag or Telephone Tag. The original message is, "I wear a striped shirt. The colors of the shirt are blue, red and yellow."
Somewhere along the line in the group, someone made a mistake. They told their neighbor what they thought they heard. "I wear a striped shirt. The colors of the shirt are BROWN, red and yellow."
Let's say that nobody else makes a mistake. When the message gets back to the originator, he will say, "That's wrong! It's BLUE not brown." Everybody gets a laugh.
If we went to each individual in the group and asked them what color they said, blue or brown, we could eventually discover what person changed the message. This is what happens in Y-DNA testing.
Over generations of the Y-DNA message being passed down, mistakes (or mutations) are created. These mutations are not life or health-threatening. "Mutation" is a scientific term used to explain a random change in the DNA.
When we refer to MARKERS, we are basically identifying a particular stripe's location on the shirt that our male test subject is wearing. (For example, the FIRST STRIPE is blue. BLUE is the marker's value.)
Somewhere along the family line a color can "randomly" change. This again is the "mutation" we refer to. If we ask each person in the circle who changed the color, we will eventually find the person who changed it. But...
The "problem" is the person that changed the color has most likely passed on. So how do we ask that person (or their DNA) if they changed the color of the stripe? Simple, we ask their male children. If their male children are passed on, we ask the male children's male children, and so on. Eventually we find male cousins or descendents of the person that had a change in their DNA "marker" or the color in their striped shirt.
But... How is this like a circle of people when there are so many cousins, some very distant?
In our Telephone Tag example, let's say the originator told their son in 1650, "I wear a striped shirt. The colors of the shirt are blue, red and yellow." Each father down the line eventually tells his son what color shirt he is wearing. (Each son is suppose to wear the same colored striped shirt as his dad.) You can see how cousins hearing the wrong message generations previously will all have the "wrong" message (or will be wearing the "wrong" colored shirt).
And to add another wrench into our example, each year a father might tell more than one male child "the message." And here is where the meat of the story lies. The one father can tell all his children the same message, but not every son will hear "blue, red and yellow." Chances are most sons will get the message right. However there is a chance one or more sons will change (or mutate) the original message. Now the "wrong" message will be passed on father to son, etc.
By creating a tree, we can identify each person's colors of their striped shirt. A trend will be revealed exposing what stripe displays a change in their shirt's colors compared to the original shirt. Two distant cousins may have the original BLUE stripe in their shirt while another distant cousin may have the changed BROWN stripe.
In the tree above we can identify two (2) things.
- Since two (2) of the three (3) cousins from the separate Son lines
wear blue, red and yellow striped shirts, there is a great chance (high
probability) the head of this line wore a blue, red and yellow striped
shirt. This is due to the fact that stripes don't easily change their
colors. The chance of two (2) brothers changing the same stripe location
to the same new color is very, very low. (This pattern identifying the
male head of line is referred to as the Halotype.)
- The blue stripe changed to a brown stripe somewhere in the "Son 3" line. We now have a means to identify the "Son 3" descendents. They all wear a brown, red and yellow striped shirt. We can therefore eliminate that these cousins descend from "Son 1" or "Son 2."
What can make Y-DNA testing ever more confusing is that many numbers instead
of a few colors are used to identify the stripes. Plus there are now 67
or more stripe locations (markers) that are identified with various colors
(or marker values) on each male cousin's shirt.
So that is all we are after. Everyone wearing the same or a very similarly striped shirt are most likely related.