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sizes of parts of a cell

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sizes of parts of a cell

Postby fantic » Tue Nov 15, 2011 9:22 am

Is the following list of items in the ascending order of their relative sizes?

nucleotide<base pair<codon<promoter<hemoglobin mRNA<hemoglobin gene<ribosome<chromosome.

tyvm
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Postby biohazard » Tue Nov 15, 2011 9:41 am

Seems to be correct.
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Re: sizes of parts of a cell

Postby zombiesagan » Tue Nov 15, 2011 3:00 pm

I agree, I don't see anything wrong with that.
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Postby fantic » Wed Nov 16, 2011 4:21 am

but how do you know ribosome>chromosome?
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Re:

Postby biohazard » Wed Nov 16, 2011 7:45 am

fantic wrote:but how do you know ribosome>chromosome?


Ribosomes are rather tiny, only something like max 30 nm in diameter in eukaryotes and bit smaller in prokaryotes. Chromosomes are considerably larger - so large that when condensed you can see eukaryote chromosomes easily with a light microscope. And to see them in a light microscope they need to be bigger than the wavelength of visible light - which is about 380 nm at its lowest end. Bacterial chromosomes are smaller, but still larger than ribosomes.
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Postby JackBean » Wed Nov 16, 2011 5:02 pm

I know that ribosomes are composed of few RNAs and several proteins, but the hemoglobin gene, to my knowledge, is quite huge (I think it contains several very long introns, doesn't it?). Cannot it be bigger than ribosome?
http://www.biolib.cz/en/main/

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Re:

Postby biohazard » Thu Nov 17, 2011 8:14 am

JackBean wrote:I know that ribosomes are composed of few RNAs and several proteins, but the hemoglobin gene, to my knowledge, is quite huge (I think it contains several very long introns, doesn't it?). Cannot it be bigger than ribosome?


Well, for starters there are several "haemoglobin genes" (e.g. genes for the alpha chains and beta globins) in humans to begin with, and as the original question does not tell us which gene exactly is in question, I assume that the main idea of the question is to demonstrate that a gene is normally larger than its corresponding mRNA product, but smaller than some other structures, such as a ribosome.

Furthermore, a haemoglobin unit consists of several subunits which are all products of their corresponding genes, and even the fully assembled haemoglobin protein is smaller than a ribosome, so I think it is safe to assume that the genes for encoding those subunits are also smaller than ribosomes.

Unless I'm mistaken, a whole haemoglobin unit has a diameter of roughly 10 nm, so it is about three times smaller in size than a ribosome. And a gene for any given haemoglobin subunit is likely to be smaller than this even if it had long introns, I assume.
Last edited by biohazard on Thu Nov 17, 2011 8:28 am, edited 1 time in total.
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Postby JackBean » Thu Nov 17, 2011 8:25 am

I guess so. Just that in all the animations are the ribosomes so small :lol:
http://www.biolib.cz/en/main/

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Re:

Postby biohazard » Thu Nov 17, 2011 8:34 am

JackBean wrote:I guess so. Just that in all the animations are the ribosomes so small :lol:


Yeah, I guess they can be considered rather tiny even on a cellular scale, since most cells can contain thousands of them or more.
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