Ancestral versus Derived

[Brunetmj]

Could someone, in simple terms, explain why Ancestral and Derived those always appear together. I know derived means "your results" by why the ancestral?
So why the necssity of those terms being used toghther?

[Stephen Parrish]

Could someone, in simple terms, explain why Ancestral and Derived those always appear together. I know derived means "your results" by why the ancestral?
So why the necssity of those terms being used toghther?

Ancestral = unmutated version of an SNP
Derived = mutated version of an SNP

Stephen

[Brunetmj]

[QUOTE]Ancestral = unmutated version of an SNP
Derived = mutated version of an SNP/QUOTE]

So if the SNP in question is present , you have the mutated version? So you do not have the SNP in question if you have the unmutated version. ?
If thats true I still do not see the purpose of reporting it that way.

[JohnG]

You can have the SNP in either ancestral or derived state.

Lets say you have SNP 1367 and the ancestral state is G. If you have G for that SNP you are ancestral and if it has changed to ,say, A your value is derived.

[Brunetmj]

So any particular SNP exists in one of two states ? Non mutated or mutated. I think I have the concept but not sure I understand the implications of one over the other. For example what is the implication of being L21 in the ancestral state rather than the derived state ?

[efgen]

Ancestral = Negative = Non-mutated
Derived = Positive = Mutated

So if you're tested for L21 and the result is negative (L21-), that means your Y-DNA has the original non-mutated (ancestral) value at the position on the Y chromosome where L21 is found. In other words, you are NOT within the L21 subclade.

If you're tested for L21 and the result is positive (L21+), that means your Y-DNA has the mutated (derived) value at that position on the Y chromosome. In other words, you ARE within the L21 subclade.

Elise

[Brunetmj]

So if you're tested for L21 and the result is negative (L21-), that means your Y-DNA has the original non-mutated (ancestral) value at the position on the Y chromosome where L21 is found. In other words, you are NOT within the L21 subclade.

Ok, this is what I originally belived. But what is wrong with just saying you are positive, or negative ,for a particualr SNP. Why is it necessary to go through the hoops of reporting an ancestral value ? That is the part I am missing. Now just what, but why?

[Zaru]

Ok, this is what I originally belived. But what is wrong with just saying you are positive, or negative ,for a particualr SNP. Why is it necessary to go through the hoops of reporting an ancestral value ? That is the part I am missing. Now just what, but why?

It's technical jargon used by scientists. Elise broke it down nicely- the upside is, you can attend a convention and speak the language!

[Brunetmj]

It's technical jargon used by scientists. Elise broke it down nicely

Yes she did. However it dosent really answer my question,which is why? Why is it necessary to report both states? I understand already that derived means you tested postive for a particular SNP. I just want to know why do you need to also report the ancestral state which states a negative.? What does that buy you? Is it just tradition? Or does it have a deeper meaning?
I really do appreciate peoples efforts to provide an answer.

[Mike_]

Is it because there is a third state - not tested

So just because you aren't positive it doesn't mean you are negative.

[efgen]

Is it because there is a third state - not tested
So just because you aren't positive it doesn't mean you are negative.

Yep, exactly! If the negative SNP results weren't reported, then we wouldn't be able to differentiate between those who are negative and those who simply haven't been tested for the SNP yet.

Elise

[Brunetmj]

So just because you aren't positive it doesn't mean you are negative.

I see! So reporting a ancestral state would mean you tested negative for the SNP AND indicate it was tested?

[1798]

Yes she did. However it dosent really answer my question,which is why? Why is it necessary to report both states? I understand already that derived means you tested postive for a particular SNP. I just want to know why do you need to also report the ancestral state which states a negative.? What does that buy you? Is it just tradition? Or does it have a deeper meaning?
I really do appreciate peoples efforts to provide an answer.

Why is it so important to you?

[Brunetmj]

[QUOTE]Why is it so important to you?/QUOTE]

Just pure curiosity. I have seen it many times and I am trying to increase my knowledge of SNP testing

[1798]

[QUOTE=Brunetmj;381907]

Why is it so important to you?/QUOTE]

Just pure curiosity. I have seen it many times and I am trying to increase my knowledge of SNP testing

In the Chromo2 raw data file all the SNPs are shown as positive or negative.