Discussion of all aspects of cellular structure, physiology and communication.
Kindly explain what makes an Egg cell start the process of embryo formation when its nucleus is replaced by a nucleus from another differentiated cell? Also, following the symmetry of Nature, could I believe that the same thing should happen using a Sperm cell? Otherwise I feel the females will have an undue advantage over the males, which I believe the symmetry in Nature should not allow?
Females have an undue advantage when it comes to cloning. A sperm does not develop into anything no matter what you do. If you wanted it to become an embryo you'd need to engineer the sperm cell so much it wasn't a sperm any more - and with current technology there is no way of doing that anyway.
The egg cell simply has all the tools for embryo production except the another set of chromosomes. These include, among other things, right enzymes and (on a cellular level) huge energy reserves, something the sperm miss.
I don't know what this symmetry of nature you are talking about is, but women could fairly easily replace all the men in the world: they can not only produce clones but also grow them in their wombs. Men, on the other hand, would be extinct within a generation if all women disappeared.
And if this sounds overly feministic to you, let me assure I'm a man and thus among the dispensable ones ;)
Thank you biohazard, for your prompt and complete reply. Regarding symmetry, I was referring to the need for a Sperm and Egg for fertilization, as per the original design of Nature, but what a sad state of affairs, that the females do appear to have an edge over males, inspite of the fact that the testosterone has been leading over estrogen all along.
Ok, now I have another question regarding cross species cloning. Recently I read about the usage of the nucleus from a human heart tissue cell to replace the nucleus of a pig's Egg cell to produce a cross species embryo. Does it mean that the nucleus used in cloning need not have to satisfy some matching criteria? Can one use freely any nucleus from any animal and egg cell from any other animal?
Well, firstly, I believe that men still have a good few thousand years or more to wage war, drink booze and sell drugs and women, play highest levels of sport and whatever manly businesses there are before we go extinct. The funny thing is that despite everything men have done during the history of mankind, women still seem to like us, so maybe we're safe after all.
Secondly, what comes to cross-species cloning, I must say that with current knowledge it is challenging enough to clone an individual even when there is no cross-species element involved, not to mention doing it with cells from different species. However, I think most mammalian eggs are pretty much similar in function, so in theory it might be possible to insert human nuclei into eggs of different species and get something out of it. I do not know for sure what "compatibility" factors there might be, since neither the nucleus or the receiving egg have immune system of their own, and cannot thus reject each other like it generally happens with xenographs (tissues from another species). Probably it comes down to enzymes: the pig egg may not have correct enzymes to fully make the foreign nucleus to work, for example.
Also, it is important to remember that if you insert a human nucleus into some other species' egg, it would still be a human embryo if it developed, not a pig-human, since the genome is entirely human. Oh, well not _entirely_, the clone would have pig mitochondria :)
Thank you biohazard for your interesting reply. Yes, the piggy experiment is mainly to use stem cells from the embryo for research purposes and not for cloning, and they have some plans to emphasize the human mitochondria in the embryonic cells, though I do not quite understand how they do it. Here is the link to that article: http://www.telegraph.co.uk/scienceandte ... ahead.html
By the way I forgot to clarify one more aspect regarding the basic cloning process. I can imagine that when two nuclei merge as in standard fertilization, some energy may be released, which could kick start the process of embryo development. But when you replace the egg nucleus with a nucleus from another cell, where does the trigger for embryo formation come from?
Also just like cloning process, is there a process to inject a haploid nucleus into an egg cell so that fertilization of the egg could take place with nuclei fusion?
A simple physical stimulus may be all it takes to kickstart the embryo development - I think they have done it even with a needle prick or a minor electric shock.
What comes to that haploid fusion, I think I have to return to that later.
Hmmh, the haploid fusion part seems to be a bit more complicated. Haploid somatic cells are routinely used to produce diploid hybrids at least in plants and fungi, but with higher animals it seems to become tricky. Apparently this has been done at least with mice when scientists have tried to fuse a haploid somatic cell into an egg in order to produce stem cells of the somatic type.
As far as I can tell, inter-species haploid fusion hasn't been done with animals, at least not with much success. Not to mention live hybrid animals. But somatic hybrids is a topic I'm not too familiar with, so I'm not 100% certain what the situation is currently.
Certain genetic elements can of course be transfered between species in order to produce hybrids, and it is actually relatively easy to do. Pigs are being tailored to produce humanised organs, for example. But with whole genomes it is quite different.
Thank you, thank you so much for that detailed reply, your name should have been biowizard !!.
Now, as regards fungi, it is a biobridge between plants and animals? Also, its cells are haploid cells. So if a fungi cell is introduced into an egg cell of an insect, I could expect the cross product of the reaction to produce an insect with a fungal characteristic ( insect larva born with a hypha), OR , a fungus with an insect characteristic ( motile fungi). I would like to hear your valuable comments about this possibility.
it wouldn't produce any kinds of organism, because yeast proteins cannot efficiently interact with animal proteins, and some proteins are present in animals and not in fungi (and vice versa). Sorry, not that simple to make freaky organisms
"As a biologist, I firmly believe that when you're dead, you're dead. Except for what you live behind in history. That's the only afterlife" - J. Craig Venter
Please, please,please, does anybody else have a different view of this topic?
Dear MrMistery, I do accept it is not so simple.In the Biology text books there is a void as far as the symbiotic relationship between Fungi and Insects are concerned. Neverthless, the insects are madly attracted to fungi, and I feel there is more than CO2 and hunger for fungal spores that attract these insects. The Bio textbooks only talk about stories of termintes and leaf cutting ants and one more type of organism that are dependent on fungi. But I think there is more to this story.
Last edited by koyal on Fri Jul 17, 2009 8:14 am, edited 1 time in total.
Well, symbiosis is a quite different thing from hybrid species. Even with lichen that is an extremely close symbiosis of an alga and a fungus the individual cells stay strictly as either fungal or algal cells; symbiosis does not form inter-species hybrids.
By simply merging haploid cells you probably cannot hybridize even a human and a chimp, since the few percents of genetical differences there are is well enough to make mismatching pairs of chromosomes and genes. That would pretty certainly prevent normal cell division. And also like MrMistery said, on enzymatical level there'd be problems as well.
If you want to make freak hybrids, I suggest you stick to transfering genes of know function into appropriate promoter regions and see what happens ;)
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