[DoctorBeaver (OP)]

OK, so we all know that cells divide again & again in order for an organism to grow. But where does the raw material come from? If you divide something you get 2 parts equal to half the size of the original. But cells don't seem to behave like that. When they divide you get 2 cells that are both the same size as the original (or, at least, that's how it appears to me when I've seen it). How does that work?

[Seany]

I always thought that it was like some sort of reproduction, but within cells.

If we look at humans, or any other animals, our babies eventually grow the same size as us. And we are all relatively similar sized, and of course, the cell wouldn't be exactly the same size among each other, but too similar to tell a major difference.

The only difference is, that humans reproduce at a slower pace, and takes longer for the new-born to develop and become our adult-size, whilst cells reproduction rate is so much faster.

I'm not sure if I'm correct in saying this way. []

[DoctorBeaver (OP)]

Seany - I think you've misunderstood what I put. I've watched film of cells dividing & when the original cell splits in half the 2 halves appear to be the same size as the original. I don't know whether it's an illusion or fact.

[Seany]

Ohhh.. It's a fact. []

[amanita]

just by chance I encountered your discussion.... as cell cycle is my favorite science topic i just could not help it not register and post my reply []
you know that part of the definition of life is metabolism (apart from the most important replication of course ), so every cell is able to grow, i.e. synthesize its basic building blocks (metabolism). []
and both replication and metabolism must therefore be tightly controlled so that the progeny receives equal amounts. Why that is? Well, one explanation is that in this way cells have the greatest chance to survive and be reproductive themselves. Also one fact that makes this point clear is the failure of this regulation machinery in diseases as cancer.
So, what do cells do? They have the so-called checkpoints. The cycle of division can therefore be divided into logically distinctive parts. In one phase cells grow until they have reached a critical size, first then are they allowed to proceed replicating the genetic material. Different proteins in this case serve as the cell's policemen. The completion of replication and the integrity of the DNA is then surveilled by a different but related regulatory network....
I hope I did not scare you with these details. Actually, all this is so beautiful if only one goes into it []
here is a nice link if you just got interested - newbielink:http://nobelprize.org/educational_games/medicine/2001/ [nonactive] []

[Seany]

Yayyyy amanita!! Hope you have fun here and come in regularly! []

[DoctorBeaver (OP)]

Amanita - thank you for that & welcome to TNS. I am already aware of the process of cell division as a result of studying possible genetic causes of ASDs. However, you still haven't answered my original question - where does the raw material for their growth come from?

[amanita]

hi to you again:) yeah, your question was actually 2 questions the raw material... well. they (cells) eat exactly as we do, actually from what we eat. i find it also totally fascinating that there is a certain type of bacterium that feeds on radioactivity:) but if you ask me, i chose chocolate

in the previous message i was trying to make the point that because of the problem you have spotted (i.e. if you divide a thing into 2 part, the halves should be equal but half the size of the original, in theory) cells have evolved mechanisms to control and compensate for this. this is one reason why life needs energy, or?

but then good to note is that during embryonic development, the first several cell divisions do not produce daughter cells that are equal to the original, but are always halves of halves of the halves:)  so, in this case you have many cells that altogether comprise the same volume as the original fertilized egg. Is this a mechanism to make the developing organism independent of its mother? And why?

but also can you explain to me what is/are ASDs and what it has to do with cell division?

[Seany]

in the previous message i was trying to make the point that because of the problem you have spotted (i.e. if you divide a thing into 2 part, the halves should be equal but half the size of the original, in theory) cells have evolved mechanisms to control and compensate for this. this is one reason why life needs energy, or?

Why should it in theory, be that the cells, when they split in half, they should be half the size of the original?

Are our babies, half the size of us when they grow into adults? At first, the cell which has just been split, is about half the size of the original cell, but then it develops and gets bigger, just like our babies do. However, their process is so much quicker than that of a human.

[DoctorBeaver (OP)]

Amanita - ASD = Autism Spectrum Disorder. There are strong indications that some ASDs may be caused by damaged DNA (transposition, inversion, ring, etc) which occurs during mitosis.

[amanita]

Seany, sorry, i meant "in theory" because some cells divide unequally... and because this logic about division holds true only from the perspective of mathematics...
one more point, about dna damage....  transpositions and inversions can accure also out of the cell cycle, in somatic cells, or not? Or, this mitosis specific damage is an ASD related event? Does it occure during development, or in the germ cells?

[DoctorBeaver (OP)]

Maybe I phrased it wrong. I meant that 1 possible cause of cell damage is faulty replication during mitosis. It can happen in any cell but, obviously, the effect will be greater if it occurs in a zygote.