Mitochondrial genomes are very stable

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Monique
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Originally posted by tyroman
is it done by a.) first removing an egg's cytoplasm and all that it contains (reticula, ribosomes, mitochondria, etc.) and then inserting all the above from a healthy cell... or b.) just remove and replace the mitochondria... or c.) just inserting healthy mitochondria? Does the donor cell have to be an egg (or even necessarily female)?
It can be done by taking out the nucleus of the donor cell and placing in the nucleus of the patient or by microinjecting cytoplasm from the donor into the egg of the patient. A person born from that will have 3 genetic ancestors, recently there was a stirup where lesbian mother's were able to both become genetic mothers of a child, by cytoplasmic transfer. Unethical, since a disease is not cured or no problems overcome, but risks are being taken.

You ask a very interesting question -again :P- whether it need to by mitochondria from an egg. I think it should be, since the egg has its own biochemical program where there is a pool of nutrients in the cytoplasm. Another cell wouldn't have such nutrients and might thus not lead to proper fertilization.. but then again.. cloning has succesfully been attempted where an organism was born from ordinary cells :)

This leads me to another question about mitochondria; do we know why evolution has selected to prevent male mDNA from entering the egg (and what happens if male mDNA is artificially injected into an egg nucleus?
I don't know.. I'd have to know more about the actual chemical process that takes place when a sperm enters the egg. It might have something to do with the fact that an egg will make its plasmamembrane impenetrable once a single sperm breaks the surface (to prevent multiple fertilizations). Probably the tail with the mitochondria just gets stuck, while the head is able to dissolve.

Where is Center for Molecular Medicine and Genetics and are you still there?
No, I am no longer there, new challenges to be faced ;)

Finally, what do you think of my hypothesis on the Swim Lesson question and how could it be tested?
Um, so you said that sperm have no evolutionary feedback which allows them to perfect -or maintain- their mitochondrial function. Thus many sperms are made to compensate for bad function.

Hmm, I once watched a sample through a microscope in a hospital where they were doing diagnostic testing. That was a long time ago though, but my impression was that sperm normally are very good swimmers. What just came up in my head, is that there might be a reason why mitochondrial DNA moved to the nucleus! Evolutionary pressure to allow for sperm to pass along good genes, which allow them to swim well :) Sounds like a good hypothesis right? Why else would this transfer have occured?

Also, I mentioned that there is evolutionary pressure in the egg itself too after it is fertilized, passing on good mitochondria. Mitochondria are just energy power-houses, there are many more genes involved in the strategic placement of the mitochondria in the sperm along the actin(?) where energy is most needed. That won't be something encoded in the mDNA, rather in the nDNA.

I also remember you asking what would happen if sperm mitochondria were injected in the egg. Nothing really :) There are reports out there that claim they measured paternal mitochondrial DNA in offspring, up to 2% I believe.

Another interesting fact: sperm know in which direction to swim :D a long time ago a posted a thread (maybe I'll be able to find it) where there was a T-crossing and sperm had to choose which way to go. About 60% went in the direction where the egg was located :)
 
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Originally posted by Monique
Yes, eucaryotic and procaryotic flagellums are different.. I am not so familiar with eucaryotic flagellums though, are they just an extention of the cell wall? Is it similar to pili in the gastrointestinal tract and the lungs?
First no, second yes :smile:.
Pili of gastrointestinal cells are much simpler structures, you could say that they’re extensions of cell wall (membrane) backed up with microfilaments (actin skeleton). I’ve uploaded some pictures hope they’ll be helpful.

Gastrointestinal cell (pili and microfilaments)pic 1

In case of lung’s ciliar epitel you really do have cilia (active movable differentiations). Which is structurally same as spermatozoid’s flagellum or other eukaryotic flagellums. I’m not expert in field of comparative cytology, but I believe that you can find same structures at sexual and non sexual cells of other vertebrates and simpler animals (as I fogy remember from my zoology classes). Eukaryotic and spermatozoid’s flagellum is backed up with microtubule skeleton, it’s structure is called 9+2, because of number and disposition of microtubules:


Structure of eukaryotic flagellum (something from my old classes:smile:) : pic 2

Flagellum is attached to cell wall with actin, spectrin and miozin filaments. Junction places with membrane are most probably locations were the ion pumps are installed, (probably they’re on -< junctions (drawed as -< and >- on the pic)) . Were we come to the easies noticeable difference between pro end eukaryotic flagellum: eukaryotic is beating , and procaryiotic is rotating!

The prokaryotic f. it totally different:smile:, and unlike euc. It rotates (rather than beating). Prokaryotic flagella are long and thin, they are anchored at one end of membranes by a complex basal body. They are composed of protein flagellin, ad driven by complex flagellar motor.

Prokaryotic flagellum: pic 3

About "mitochondria discussion" - haven’t read all - too long - Although I more prefer that kind of discussion than this structural.

P.S. to administrator: you should enable code for all rooms except general discussion, because I believe you’ve disabled It just because of g. discussion.
[PLAIN] is useful, and if you enable it in that way, it want take you a lot of bandwidth, but it’ll help and increase quality of discussion.

p.s.s. pictures aren't available for now, FTP server is down[b(] , so I'll upload as son as they got FTP going ...
 
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  • #28
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server is barley up, nevertheless, pictures are up too...:smile:
 

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