Organelles in cellular reproduction

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Organelles in cellular reproduction

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1richardbsmith
Jun 19, 2012, 9:31pm

A couple questions about the reproduction of organelles.

When a nucleus splits, what makes a new set of organelles? Do they each split simultaneously with the nucleus into the new cell?

When eukayotes first took on the partner cells that became the organelles, how did this arrangement first reproduce itself?

2stellarexplorer
Jun 19, 2012, 11:21pm

The genome of the daughter cells make whatever organelles are needed. The organelles in the original cell end up incorporated into the daughter cells as well in roughly equal numbers.

3richardbsmith
Jun 19, 2012, 11:28pm

I thought the organelles had separate DNA and would have to split separately.

4LolaWalser
Jun 21, 2012, 4:18pm

Mitochondria and chloroplasts are the only organelles with own genomes, and yes, they can (do) replicate independently from the nuclear genome. The rest--vesicular organelles--duplicate by fission. I can't vouch for details of biogenesis regarding different kingdoms... much water has passed under the bridge since undergrad.

When eukayotes first took on the partner cells that became the organelles, how did this arrangement first reproduce itself?

Presumably, nothing more was needed than that the new symbiont remain functional (undigested/unmolested) and capable of self-replication.

5richardbsmith
Editado: Jun 21, 2012, 5:37pm

Thanks LolaWalser. Every account I read about cellular reproduction leaves me with that question about how the mitochondria and chloroplast organelles reproduce simultaneously with the cell nucleus.

Maybe a protein taps them on the shoulder and says NOW.

Another question that I have not found answered is where do the duplicate DNA strands come from, the replicated chains that join the two strands of split DNA.

Somewhere I will find that explained - or it may be in a text that is beyond my knowledge level.

6LolaWalser
Jun 22, 2012, 8:55pm

I doubt it's a protein, but some "general oversight" control probably exists (could be something as simple as ion environment of the cell). But, the duplication of mitochondria and chloroplasts isn't necessarily tied to that of nuclear DNA, I remember at least for mitochondria, they can proliferate in response to a greater need for energy, in athletes' muscles, say.

where do the duplicate DNA strands come from, the replicated chains that join the two strands of split DNA.

This description is confusing, so I'm not sure what you are asking. As the replication fork progresses (think of a zipper unzipping, giving rise to a Y-shaped structure), daughter DNA chains are bound to parental chains, there is nothing binding the parental strands (what you call "split DNA") behind the replication fork. Two separate DNA chains are arising from one.

Have you looked up DNA replication? A diagram may answer it all for you most economically. I'd do it, but I must go, sorry.

7richardbsmith
Jul 3, 2012, 7:56am

From What Evolution Is

the first eukaryote originated by a symbiosis of an archaebacterium and then by a chimaera formation of the two symbionts. This is why the new taxon Eukaryotes combines characteristics of both archaebacteria and eubacteria

I think the answer to my question (how the organelles with distinct DNA replicate with the main cell) may be related to the process of chimera formation.

8LolaWalser
Jul 3, 2012, 2:20pm

Don't get stuck on words--follow the idea. Science isn't Scripture. Mayr was a decent enough writer, but that sentence isn't one of his glories.

First, what does he mean by chimaera? The resulting eukaryotic cell, because it contains two separate lineages. Why does he call it that? To signify that a transition has occurred from one state (symbiosis) to a permanent inheritable merging: "symbionts" (plural) to "chimaera" (singular).

So your "process of chimaera formation" is just a more tortuous way of referring to two organisms entering into symbiosis--it's still vague, not some more "technical", mechanistic thing.

We don't know the details of how this happened--we know that it happened.

I think the answer to my question (how the organelles with distinct DNA replicate with the main cell) may be related to the process of chimera formation.

As I said above, organelles don't necessarily duplicate in sync with the cell, so your question is badly posed.

You could search www.pubmed.gov for papers on mitochondrial etc. duplication. www.pnas.org is searchable for full papers up to the most recent six months--I recommend searching on "(your terms of interest) AND review" to pull up articles summarising research.

9richardbsmith
Editado: Jul 3, 2012, 2:56pm

The chimara formation was a phrase that he did not define (and I checked the glossary in the book). I was totally unsure about it, but did find some information on chimera formation on the web. It relates more to different animals exchanging cells, especially the mother and the fetus or between twin fetuses. Although I am sure you already know more about all this.

The idea or process of symbiosis may be more precisely descriptive.

lolawalser, I actually did not think I was asking questions about unknown details. I just thought I had missed some points that I could get cleared up with a couple questions.

I will keep looking. I found this book, but I am positive it will be well over my head.

http://www.librarything.com/work/2382514

I have a good biologist friend, I may try to corner him at church this Sunday.

10LolaWalser
Editado: Jul 3, 2012, 3:12pm

Again--don't get stuck on words. Chimaera is a mythological beast composed of body parts from different animals. In science the term occurs in different contexts, and you'll just get terribly confused if you try to relate them all to each other! It's the basic concept that matters. So, we speak of chimeric genomes when these are composed of genes from different lineages, of chimeric proteins, of chimeric tissues, of chimeric organisms etc.

The idea or process of symbiosis may be more precisely descriptive.

Er, no. Again, "chimaera" is a concept, and in each of the cases I mentioned it can be precisely described.

Mayr was using the term in relation to the eukaryotic cell conceptually, it's not some reserved term for it.

I think I'd suggest a good basic cell biology textbook for you first--The Cell, for instance. (See touchstone for full title.) If I may so, I think your grasp of the general picture is the bigger problem than lack of detail.

11richardbsmith
Jul 3, 2012, 3:15pm

No doubt I need a better grasp of the bigger picture. Thanks,

12LolaWalser
Jul 3, 2012, 3:25pm

You're welcome. A good textbook such as Alberts is a necessity especially if you get tempted by myriad side-questions. There's no point in going for those to more specialised volumes if, say, you aren't clear on basic processes or terminology (how does DNA replicate, what is a chimaera etc.)