Y-DNA mutations

[JPHutchins]

I have a question regarding Y-DNA mutations. I would like to pose this question to those of you who have more knowledge of the subject (just about anyone).

For purpose of this hypothetical question let’s assume that a father has 3 natural sons and all four (father and sons) have had their Y-DNA tested. Let’s also assume that Marker “X” is known to be a rapidly mutating marker. The father’s results returned with a value of “14” for marker X. We know that mutations occur at generation gaps. So could any or all of the following scenarios result?

1. Father “14”, Son #1 (b:1975) “14”, Son #2 (b: 1978) “14” and Son #3 (b: 1980) “14”
2. Father “14”, Son #1 “14”, Son #2 “15”, Son #3 “14”
3. Father “14”, Son #1 “15”, Son #2 “14”, Son #3 “15”
4. Father “14”, Son #1 “15”, Son #2 “15”, Son #3 “15”
5. Father “14”, Son #1 “14”, Son #2 “15”, Son #3 “15”

The question is whether the mutation is random among the offspring, or “once mutated, always mutated”?

[Frederator]

Any and all of those scenarios are possible.

Anecdotally, my father is 18 at #458, my oldest brother is 17 at #458 and I, the third son and sixth child, am 18 at #458.

Others may refer you to more scholarly discussions, but the bottom line is that random is random. There are various levels of probability that describe the relative likelihood of each scenario, based on the observed mutation rate and the standard deviation in the general population, but those numbers are of pretty limited use in the context of one specific marker for one specific family.


[QUOTE=JPHutchins;298603]I have a question regarding Y-DNA mutations. I would like to pose this question to those of you who have more knowledge of the subject (just about anyone).

For purpose of this hypothetical question let

[Zaru]

Yes.

Anything is possible but some are more probable. My brother and I are a GD of 1 at 25 markers. He has only 25 markers tested and I have all 67. Who knows if our GD is greater?

The point is, mutations can occur at any locus in any given generation. Why that possibility? Because we do not have an example of the first YDNA sample in the data base, that alpha spot where there were no mutations to speak of. Hence, we have no point of reference in the database. Some strs mutate quicker than others, and reverse mutations are rare but not impossible.

[aeduna]

The question is whether the mutation is random among the offspring, or “once mutated, always mutated”?

I am not a biologist, but... I would assume that these mutations are happening at the point where each individual sperm is being created. So yes, you could potentially get different values for different progeny. I would imagine that its statistically unlikely, even for a fast mutating SNP with an less stable value.

[192971]

"Once mutated, always mutated" cannot be operative here, due to following reasons:

All the sperm generating tissue cells of an individual man cannot suddenly mutate the same way. (Except if it is a miracle.)

A random mutation happening in generation of a singular sperm cell cannot affect the generation of other sperm cells.
(Compare: A result of tossing a coin does not affect the result of some other coin tossing.)

There cannot be any memory of a random mutation in the body once the mutated cell(s) have disappeared from it.
(Well, a tencency towards that a particular mutation happens again could exist, but it is a different matter.)