Nucleoid and Nucleosome

[Ghaz]

People can anyone help me to understand the difference between nucleoid and nucleosome?

[ewmon]

What have you found so far?

Have you looked in Wikipedia?

Have you tried googling them?

[Ghaz]

yes I have tried everything .I take forum as my last option.The following is all I get as the difference.Help me to know more differences.

 

Nucleosomes are the basic unit of DNA packaging in eukaryotes, consisting of a segment of DNA wound around a histone protein core while nucleoid (meaning nucleus-like) is an irregularly-shaped region within the cell of a prokaryote that contains all or most of the genetic material.^[

What have you found so far?

Have you looked in Wikipedia?

Have you tried googling them?

[ewmon]

Both words describe the compact structures of DNA found in living cells. The names are different to distinguish between how eukaryotes and prokaryotes store them in their compact forms. Because DNA's serial structure (that is, its information forms one-dimensional sequences), and because these sequences of one-dimensional information are many, many times longer than its cell, the DNA must be compacted into tight three-dimensional structures.

 

The DNA in eukaryotes, which are wrapped around histone proteins, are called nucleosomes. The DNA in eukaryotes is linear, and nucleosomes fold through a series of successively higher order structures to eventually form a chromosome.

 

The DNA in prokaryotes, which form a mass, are called a nucleoid. Most DNA in prokaryotes is circular, and they are supercoiled to keep them gathered together.

 

If this wasn't what you wanted to know, please ask more questions.

Edited January 25, 2012 by ewmon

[Ghaz]

thank you v much .But after a lot of research i Got the following answer;

nucleoid :

 

 

1.Nucleoids are found in prokaryotes.

 

2.it is an irregularly shaped region within the cell and contains aal or most of the genetic material.

 

3.it is composed of nucleoid protein which helps to maintain the supercoiled structure of nucleic acid.

 

4.It contains small amount of RNA.

 

 

nucleosome:

1.it is found in eukaryotes.

 

2.nucleosomes are the basic unit of DNA packaging in eukaryotes,consisting of a segment of DNA wound around a histone core.

 

3.it is composed of histone proteins which acts as a spool around which DNA winds and thus enabling the compaction necessary to fit large genomesof eukaryotes inside nuclei.

 

4.it doesnt contain RNA.(having doubt in this:( )

 

this i made after studying about nucleosomes and nucleoid ...........Please check it ands do the corrections.

 

Both words describe the compact structures of DNA found in living cells. The names are different to distinguish between how eukaryotes and prokaryotes store them in their compact forms. Because DNA's serial structure (that is, its information forms one-dimensional sequences), and because these sequences of one-dimensional information are many, many times longer than its cell, the DNA must be compacted into tight three-dimensional structures.

 

The DNA in eukaryotes, which are wrapped around histone proteins, are called nucleosomes. The DNA in eukaryotes is linear, and nucleosomes fold through a series of successively higher order structures to eventually form a chromosome.

 

The DNA in prokaryotes, which form a mass, are called a nucleoid. Most DNA in prokaryotes is circular, and they are supercoiled to keep them gathered together.

 

If this wasn't what you wanted to know, please ask more questions.

[ewmon]

nucleosome:

1. it is found in eukaryotes.

 

2. nucleosomes are the basic unit of DNA packaging in eukaryotes, consisting of a segment of DNA wound around a histone core.

 

3. it is composed of histone proteins which acts as a spool around which DNA winds and thus enabling the compaction necessary to fit large genomes of eukaryotes inside nuclei.

 

4. it doesnt contain RNA.(having doubt in this)

Why should nucleosomes contain RNA?

 

Eukaryotes use a method of reducing the maximum dimensions within which the long strand of DNA will fit to allow for its storage and use in the nucleus. To realize this goal, the DNA is wound around histone proteins which cluster in a mass called a nucleosome.

 

These nucleosomes reside in the nucleus, which is a compartment (basically a simple bag) within eukaryotes whose purpose is to house and maintain the integrity of the DNA and to house and control the materials used in the transcription process, whose result is newly-formed RNA.

 

So, RNA does exist in the nucleus, although not within the nucleosomes. There is no readily apparent reason for RNA to be part of the nucleosomes.

 

I hope this explains away your doubts about nucleosomes not containing RNA.

[CharonY]

While it should be clear, I would like to emphasize that nucleoids is not the functional equivalent to nucleosomes (just because the two are contrasted here).

[ewmon]

Yet are they not the compact forms by which DNA exists in living matter?

[CharonY]

I would not think of it that way. A nucleosome is only a very limited area of the chromosome, whereas the nucleoid contains the whole. Also functionally nucleosomes shift around to facilitate transcription, other mechanisms are in place in various areas of the nucleoid.

Also a nucleoid is not a compact form per se, there is a lot of relaxing and coiling going on, etc etc.

 

To put it simple, a nucleosome is a means to locally organize the chromosome, whereas a nucleoid is functionally closer the whole nucleus. Bacteria have no need for that level organization that many eukaryotes have. Nonetheless, they also have certain proteins there that fulfill scaffolding functions. It is just not researched as well yet, as the level of organization is lower and the effects less dramatic and less accessible.

Edited January 27, 2012 by CharonY

[raid517]

But what about DNA primase? During the replication of DNA small segments of primer RNA are laid down, so surely even though it's only for a short while, the nucleosome of Eukaryotes does contain a small amount of RNA?

[Ghaz]

thanks

I would not think of it that way. A nucleosome is only a very limited area of the chromosome, whereas the nucleoid contains the whole. Also functionally nucleosomes shift around to facilitate transcription, other mechanisms are in place in various areas of the nucleoid.

Also a nucleoid is not a compact form per se, there is a lot of relaxing and coiling going on, etc etc.

 

To put it simple, a nucleosome is a means to locally organize the chromosome, whereas a nucleoid is functionally closer the whole nucleus. Bacteria have no need for that level organization that many eukaryotes have. Nonetheless, they also have certain proteins there that fulfill scaffolding functions. It is just not researched as well yet, as the level of organization is lower and the effects less dramatic and less accessible.

 

thanks for th help

Why should nucleosomes contain RNA?

 

Eukaryotes use a method of reducing the maximum dimensions within which the long strand of DNA will fit to allow for its storage and use in the nucleus. To realize this goal, the DNA is wound around histone proteins which cluster in a mass called a nucleosome.

 

These nucleosomes reside in the nucleus, which is a compartment (basically a simple bag) within eukaryotes whose purpose is to house and maintain the integrity of the DNA and to house and control the materials used in the transcription process, whose result is newly-formed RNA.

 

So, RNA does exist in the nucleus, although not within the nucleosomes. There is no readily apparent reason for RNA to be part of the nucleosomes.

 

I hope this explains away your doubts about nucleosomes not containing RNA.

[CharonY]

But what about DNA primase? During the replication of DNA small segments of primer RNA are laid down, so surely even though it's only for a short while, the nucleosome of Eukaryotes does contain a small amount of RNA? <br class="Apple-interchange-newline">

 

Not only that, of course during transcription, there will be RNA present. However, functionally the nucleosome is not assumed to be actively replicating or transcribing. In fact, nucleosomes appear to be displaced during transcription, for instance.

Note that the nomenclature are context-driven and just convenient terms to give certain elements specific names. Usually, they do not capture the complete dynamics of what really is going on.

[Santalum]

Not only that, of course during transcription, there will be RNA present. However, functionally the nucleosome is not assumed to be actively replicating or transcribing. In fact, nucleosomes appear to be displaced during transcription, for instance.

Note that the nomenclature are context-driven and just convenient terms to give certain elements specific names. Usually, they do not capture the complete dynamics of what really is going on.

 

Is it that the histones are of a fixed length and there are many of them per chromosme? The combination of one histone chain and that part of the chromosome that is coiled around it is refered to as a nucleosome and that there are many nucleosomes per chromosome? And the nucleosomes collectively form the chromosome?

Edited January 30, 2012 by Santalum

[CharonY]

The combination of one histone chain and that part of the chromosome that is coiled around it is refered to as a nucleosome and that there are many nucleosomes per chromosome?

 

This part is correct, however, one would probably not say that the chromsome consists of nucleosomes, as there are also non-packaged parts of the chromosome (especially active areas). The nucleosome is really a term to refer to basic DNA packaging within the chromosome.

[Santalum]

This part is correct, however, one would probably not say that the chromsome consists of nucleosomes, as there are also non-packaged parts of the chromosome (especially active areas). The nucleosome is really a term to refer to basic DNA packaging within the chromosome.

 

I see. That much was a bit of an educated extrapolation from what I do remember of genetics 201 and biochemistry 201 as the precise details about DNA structure have gotten a bit rusty over the years.