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Tuesday, November 8, 2011

posted 4th Reply to, "Inheritance from 10th to 12 generation ancestors

[quote name 'MMaddi']
OK. Your quote of my question to you and your answer clarify what you think is happening. Reread my post and other posts which have given you information about how the various types of DNA are transmitted and what they do or provide. There is nuclear DNA - the x, y and autosomal chromosomes - and mitochondrial DNA, outside the nucleus. I've bolded the last sentence I've quoted from you to show that you mistakenly believe that somehow there is a connection between mtDNA and a woman's x and that only the woman's x from her mother can be transmitted to her children. This is what I thought your misconception is.

Again, mitochondrial DNA and the x chromosome have different functions, are located in different parts of the cell and are not transmitted in the same way, especially since the x recombines in a woman, just like the autosomal chromosomes. No one here disagrees with you that mtDNA does not recombine and is transmitted solely from a mother to her children, sons and daughters, and then transmitted unchanged only by her daughters. What you are misunderstanding is the x chromosome, mixing it up in your mind, it seems, with mtDNA.

You wrote, "I'm dismayed that talking to a non-professional is so confusing for you; I may not know everything that you do, but how could you miss my point? You took the conversation away from the OP's question, & tried to school me in biology." I'm a non-professional myself. I guess you would call me an educated layman. But I'm able to grasp the concepts involved by learning from others with more knowledge. With all due respect, you could do the same, if you would not be so committed to defending mistaken ideas.

My statement which you highlighted is actually germaine to the issue here:

"How would the X received from their fathers ever be capable of carrying their own mothers' mitochondria, which women then pass along to their own children?)"

Admittedly, it's poorly phrased, but as you have pointed out yourselves - I'm not a DNA scientist.

Also, in that post I attempted to answer several of you at one time. So you might be confused about ~which~ X chromosome "the X" is referring to; do you realize what I'm talking about?

I'm referring to the one & only X chromosome that is contained in each ovum, the single cell which combines with the father's sperm (containing either an X or a Y chromosome, not both), to make babies.

Women pass their mtDNA along to their children in that ovum with that one X chromosome. Which copied X (the one she inherited from her father, or the one she inherited from her mother) is in those eggs?

I maintain that it's the maternal X chromosome, the one that is inherited repeatedly down through potentially vast numbers of generations of a family, in an individual's direct maternal lineage. Why do I believe that?

Because, mothers "typically" or "normally" pass their own maternal mtDNA, generally unchanged/unrecombined, to all of their biological offspring. And the coding for mtDNA is found in the nuclear DNA, not in the mtDNA itself (which contains codes for other sorts of body/life processes.

Every mother's specific maternal mtDNA's structure is encoded within the nuclear DNA or genes of her cells. I assume that means also the ova, right? So the paternal X chromosome copies inherited from her father shouldn't be the same ones that are found in ova, for that to happen correctly.

Lol, but I was taken by surprise when you all began talking about recombination, since mtDNA doesn't "normally" recombine. However, many of you continued to insist that it does. Someone even said it's the rule, not the exception. And you are entitled to your beliefs.

But I provided solid evidence that mtDNA doesn't recombine, nevertheless. I don't pretend to know everything, but I don't judge what people tell me by their professional work qualifications. Instead, I try to pay close attention to what they're saying.

I must say that I did learn quite a lot here, & in my prior post I shared some of it with you, with references. All the chatter about X chromosomes & recombination, etc., etc., forced me to do even more research on my own, & I find the subject to be quite fascinating.

mtDNA contains a relatively small number of genes, compared to nuclear DNA;

and, the coding for mtDNA is located in the nuclear genes.

I stand by my original claim that mtDNA rarely (if ever) undergoes recombination; and contributes set, relatively fixed percentages of DNA to practically every individual offspring in any direct maternal lineage.

That is one piece of the equation, suggested by the OP's question posed in the title of this thread. (I also learned on my own, that male (Y) DNA chromosomes tend to lose genes somehow, over similarly long time periods, in their paternal lineages; another part of the equation...)

Johi, I'm Native American through my direct maternal lineage; AND my mtDNA is haplogroup W. You'll just have to figure that one out. Your statement, that I'm not NA "because W is 'European'" sounds quite ridiculous to me. But, that is because I know the true facts of the matter.

My claim probably sounds ridiculous to you, because it seems you accept without question or further investigation, government funded 'scientific' studies of Native American DNA & inheritance, which are often quite ~biased~ & sometimes very outdated.

Biased and / or outdated 'science' isn't real science. Otherwise (if it was, iow) the world would never enjoy news of any surprising discoveries. We would never hear of any corrections or adjustments in conventional, consensuous, commonly utilized  knowledge.

Scientists & educators used to teach that the Sun is the center of the Universe; the Earth the center of our solar system, things like that. But knowledge is dynamic, not static. It's gained mostly by thought: thinking; not strictly by reading texts which may sometimes be flawed (even with typos, etc.); nor necessarily from paid educators or professional experts who are only human, after all (like yourself, I presume). Every scientific conclusion is ~hypothetical~: they're always subject to ~change~, by way of further investigation / research or through serendipitous discoveries.

And the 'Out of Africa' theory of Human origin hasn't been satisfactorily disproven, imo; thanks to the genuinely earnest study of mtDNA by the early pioneers of DNA research. However, I'm sure there's an amazing amount of knowledge about Human origins & DNA yet to be discovered. And probably much more than that, which we may not ever know.

To conclude this post: 1) mtDNA seems likely to retain most of its original DNA over many, many generations, because it doesn't normally recombine, but is inherited practically unchanged, through the maternal lineage.

2) Ydna apparently gradually ~loses~ genetic material (genes, I suppose), over time, along paternal lineages. I suppose that might be due to all the recombination that goes on with it.

3) And although these two basic factors certainly must display varying rates, depending on circumstances & in different families, they must also significantly effect the percentage amounts of DNA retained in individuals from their ancestors of 10-12 generations back in time.

(As you know & have politely pointed out, I'm not prepared to discuss the finer points of recombination with you. But feel free to believe as some of you stated above, that ~inherited~ mtDNA recombines, lol.)

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