cell reproduction?

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deostroll
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cell reproduction?

Post by deostroll » Mon Jul 03, 2006 4:47 pm

I believe that a cell is capable of reproducing both ways - i.e. either by mitosis or meosis.

This begs me to ask, how does the cell know when to mitosis or when to meosis?

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Post by mith » Mon Jul 03, 2006 6:09 pm

only germ cells undergo meiosis
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Post by herb386 » Mon Jul 03, 2006 6:47 pm

The decision is usually made in response to the external environment in unicellular organisms and in response to hormones in multicellular organisms.

In multicellular organisms certain cells undertake the germ cell fate during development. These cells then undergo mitosis to increase their numbers in response to certain signals (like growth hormones) or they undergo meiosis in response to other signals.

Yeast cells undergo meiosis in response to the extracellular environment. They produce spores when they run out of nutrients or can't keep dividing for some other reason. The default is mitosis though so they will do that most of the time.

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Post by deostroll » Tue Jul 04, 2006 4:40 am

herb386 wrote:Yeast cells undergo meiosis in response to the extracellular environment. They produce spores when they run out of nutrients or can't keep dividing for some other reason. The default is mitosis though so they will do that most of the time.


Yes, even bacteria is known to do this. But why do they do so? I mean to ask is there any advantage forming spores?

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Post by deostroll » Tue Jul 04, 2006 4:55 am

herb386 wrote:The decision is usually made in response to the external environment in unicellular organisms and in response to hormones in multicellular organisms.


I was expecting someone to find a fault in my question. I am asking this question because obviously I don't have that much knowledge. Given that many cell species exist, can any one cell you take reporduce both ways?

mithrilhack wrote:only germ cells undergo meiosis


First of all what are these germ cells? Are they different from other cells only because they reproduce via meosis?

So these germ cells won't ever mitosis? But do germ cells have a point if they do? I don't think germ cells have the requirement of replacing worn out cells! Hope I'm right? :?

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Post by deostroll » Tue Jul 04, 2006 5:02 am

Oh by the way that hormone thing kind of makes sense. But who had discovered that fact?
PS: I happen to be a philosopher, rather than a true scientist...

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Post by herb386 » Tue Jul 04, 2006 9:38 am

The point of forming spores is that they are able to survive environmental conditions that would kill the normal cells. If, for example, yeast cells run out of nutrients or the temperature gets too high then the cells form spores that can survive the environmental change. When the environment becomes favourable again the spores turn back into cells which can fuse to reform diploid cells.

In response to your other questions, not all cells are able to undergo meiosis. In multicellular organisms only germ cells are able to do this. Germ cells are a group of cells within an organism which are defined early in development. Their function is to produce gametes and so they are the only cells in the organism that will be able to pass their DNA to the next generation.

I'm afraid I don't know who discovered the hormone stuff but I should think quite a few people were involved in it. Try searching on pubmed if you want to know more.

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