Two different kinds of DNA?

Factual Questions
1

What is the difference between DNA and Mitochondrian DNA? How can someone map the Mitochondrial DNA of a creature ( as is currently being done with Neanderthal man ) but say that without the regular, or “global” DNA, one could not attempt to clone or reproduce anything of that species.

Do we all have two kinds of DNA, both of which are necessary in order for our species to develop from zygote to human baby?

Google is frequently our friend, but searching the key words in this query has brought me to scientific papers that are well beyond me. Hence, my query here.

Cartooniverse

2

[QUOTE=Cartooniverse]
What is the difference between DNA and Mitochondrian DNA? How can someone map the Mitochondrial DNA of a creature ( as is currently being done with Neanderthal man ) but say that without the regular, or “global” DNA, one could not attempt to clone or reproduce anything of that species.

Do we all have two kinds of DNA, both of which are necessary in order for our species to develop from zygote to human baby?

Google is frequently our friend, but searching the key words in this query has brought me to scientific papers that are well beyond me. Hence, my query here.

Cartooniverse
[/QUOTE]

Okay, Mitochondria are parts of living cells that, in a lot of ways, act as seperate, symbiotic one-celled life forms. They function as the main ‘power plant’ of the cell - taking in simple food components like glucose and using the most of the energy of those compounds to build something called ATP that the rest of the cell can run off of. If it weren’t for this interaction between mitochondria and the rest of a creature, both halves would starve - the creature would be able to move around, get food, break it down, but be unable to actually use the blood glucose to sustain itself for any level of time - and without the glucose, the mitochondria would die too.

So, because they’re constructed as seperate life forms, mitochondria do have their own DNA, which doesn’t really have to do with anything but a mitochondrion’s specialized function in energy conversion. The reason mitochondial DNA is used in mapping is that it isn’t being endlessly split in celular meiosis and recombined in sperm-egg conception - the eggs mitochondria are the ones that are copies and used for an embryo. (I’m not sure offhand if sperm manage to do without mitochondria or if theirs are just discarded.)

So - regular human DNA has information on all kinds of specialized details without which we wouldn’t be human - and the same for regular canine DNA, regular sparrow DNA, regular trout DNA - all of it has information on the specific characteristics of that lifeform. All of these species carry mitochondrial DNA that is much more similar, though not identical, because mitochondria do occasionally mutate.

And yes, without both kinds of DNA, we wouldn’t be able to develop, because the mitochondrial DNA is necessary for an embryo to use the blood glucose and other food components provided by the mother over the umbilical cord - but as I said, energy conversion is pretty much all that the mitochondrial DNA does. It won’t help with growing fingers or saliva glands or brain cells or everything else that’s built into the main human genome.

Hope that this helps.

3

Also, mitochondria are passed down from mother to child down the ages. They have proved maternal ancestry using mitochondrial comparisons.

[QUOTE=Wikipedia]
The fact that mitochondrial DNA is maternally inherited enables researchers to trace uterine lineage far back in time.
[/QUOTE]

[SUB]Yeah, I know, Wikipedia, but it serves the purpose of explaining what I am saying. [/SUB]

4

Chrisk, that is exactly what I was hoping for. Thank you so very much. It is in the way I was “hearing” it.

I thought that it was a type or component of our regular DNA, not specifically the DNA of the mitochondrions. That word resonated faintly from Jr. High biology.

Much obliged.

5

Good summary by chrisk.

As the Wikipedia article mentions, mtDNA has a higher mutation rate than nuclear DNA, and thus can be used to identify changes over a shorter period of time.

As has been mentioned, mitochondria are thought to have originated as bacterial-type symbiotic organisms within early eucaryotic (non-bacterial) cells. Likewise the organelles in plants that contain chlorophyll, the chloroplasts, also seem to have originated as symbionts and have their own DNA.

6

[QUOTE=Colibri]
As has been mentioned, mitochondria are thought to have originated as bacterial-type symbiotic organisms within early eucaryotic (non-bacterial) cells. Likewise the organelles in plants that contain chlorophyll, the chloroplasts, also seem to have originated as symbionts and have their own DNA.
[/QUOTE]
Lest folks get too strong an impression that mitochondria and chloroplasts can still behave as quasi-independant organisms, it should be emphasized that the genomes of these things are tiny. Most of the proteins involved in mitochondrial ATP synthesis and chloroplastic carbon fixation are coded for by nuclear genes, and imported to the organelles. Human mitochondrial DNA for example, codes for just 13 proteins and 24 RNAs, while the minimal free living bacteria requires about 182 genes.

7

So … mitochondrial DNA is the only “constant” DNA for tracing lineage over a seriously long period of time…

What if the hypothetical neander - human cross was always male neander female human? would we get any ‘legacy’ neanderthal that would be specifically neander? or would we only get the human maternal mitochondrial DNA [since that seems to be the only DNA they seem to be looking for…] and unjustly figure that all the dna was human because we cant really trace male bog standard DNA as being any specific lineage?

not sure if i am being clear or not…but going by the other threads on neanders passing for human point out the neander physical differences to look for, and I have seen LOTS of mid facial prognathic people, many others with the bone ‘bun’ and brow ridges, and receeding chins in addition to the mid facial shape, and many with the receeding chin and brow ridges.

Heck, as I have said before, mrAru has many physical quirks fitting neander body types …

Anybody thought that the melungean bone bun is a neander holdover?

8

[QUOTE=chrisk]
So - regular human DNA has information on all kinds of specialized details without which we wouldn’t be human - and the same for regular canine DNA, regular sparrow DNA, regular trout DNA - all of it has information on the specific characteristics of that lifeform. All of these species carry mitochondrial DNA that is much more similar, though not identical, because mitochondria do occasionally mutate.
[/QUOTE]

Colbri: Taking this a bit further, isn’t it the case that we sometimes clone animals using the nucleus of one species inserted into the ovum of another species (from which the nucleus was removed) and so the resulting animal has mtDNA from the donor species, not its own species? Any idea how often this has been done, and how distantly related the two species have been?

9

[QUOTE=aruvqan]
So … mitochondrial DNA is the only “constant” DNA for tracing lineage over a seriously long period of time…

[/quote]

No. There is a project that uses the y chromosome to trace human migration through the male line. There’s a book on it called The Journey of Man by Spencer Wells.

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[QUOTE=aruvqan]
What if the hypothetical neander - human cross was always male neander female human? would we get any ‘legacy’ neanderthal that would be specifically neander? or would we only get the human maternal mitochondrial DNA [since that seems to be the only DNA they seem to be looking for…] and unjustly figure that all the dna was human because we cant really trace male bog standard DNA as being any specific lineage?
[/quote]

You’re right-- we wouldn’t. And that’s one reason why the Neanderthal Genome Project is so interesting.

We’re very similar to Neanderthals genetically, and you’ll see overlap of some features even without interbreeding. But we wouldn’t see those features so widely distrbuted around the globe if we got them from Neanderthals, because they only lived in Europe and Western Asia. Still, we may just find “Neanderthal genes” in our genome yet. Some scientists think they already have, but there isn’t a concensus formed around a single answer yet.

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[QUOTE=John Mace]
We’re very similar to Neanderthals genetically…
[/QUOTE]
Only insofar as the extremely limited sequence data permits any conclusions at all.

12

[QUOTE=Squink]
Only insofar as the extremely limited sequence data permits any conclusions at all.
[/QUOTE]

Not really. You could infer that with a great deal of confidence from the simple fact that we only split off from each other about 500k years ago (pretty firmly established at this point).

13

[QUOTE=John Mace]
(pretty firmly established at this point).
[/QUOTE]
Not with only material from a couple of bone fragments sequenced.
We need a bigger sample to draw such firm conclusions.

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[QUOTE=Squink]
Not with only material from a couple of bone fragments sequenced.
We need a bigger sample to draw such firm conclusions.
[/QUOTE]

We’ve got mtDNA and nuclear DNA (warning: PDF) data that points to pretty much the same time frame. Besides, even if we were double that time, say 1M years, we’d still come to the same conclusion. There just hasn’t been that much time since the ancestors of Neanderthals entered Europe and were, presumably, isolated from other human populations.

15

[QUOTE=John Mace]
Colbri: Taking this a bit further, isn’t it the case that we sometimes clone animals using the nucleus of one species inserted into the ovum of another species (from which the nucleus was removed) and so the resulting animal has mtDNA from the donor species, not its own species? Any idea how often this has been done, and how distantly related the two species have been?
[/QUOTE]

Yes, the usual cloning procedure involves inserting the nucleus from a somatic cell of one individual into an egg cell taken from another. Such clones are not completely identical to the nuclear donor, since they differ in their mtDNA (unlike identical twins, which are derived from the same fertilized egg).

The only cross-species cloning of this type I am aware of involved genetic material of Asian wild cattle, gaur and banteng, and eggs cells of domestic cattle. These species all belong to the same genus, and are interfertile.

African wildcat clones have also been produced using egg cells from domestic cats, but these are technically the same species.

It is unknown what the effect of using nuclear and mtDNA from more distantly related species might be.

16

[QUOTE=chrisk]
(I’m not sure offhand if sperm manage to do without mitochondria or if theirs are just discarded.)
[/QUOTE]

Discarded. The mitochondria in a sperm cell are concentrated around the base of the tail, where all the energy is needed. Once the egg is reached and one burrows its way in, only the head part fuses, letting nuclear material in. The tail is just there to propel the sperm all the way to the egg, so once the job is done, it’s left behind.

17

[QUOTE=Antigen]
Discarded. The mitochondria in a sperm cell are concentrated around the base of the tail, where all the energy is needed. Once the egg is reached and one burrows its way in, only the head part fuses, letting nuclear material in. The tail is just there to propel the sperm all the way to the egg, so once the job is done, it’s left behind.
[/QUOTE]
I have a vague memory of hearing within the past 5 years or so some talk that some of the male cytoplasmic material does or can make it into the fertilized egg and end up somehow influencing development in a way that they previously thought only the egg’s cytoplasm controlled. I don’t remember if they were talking about mitochondria or other factors or both. I know that’s frustratingly vague, but does anybody remember anything like this?