sarah5
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hello
What is the difference between nucleosome,chromosomes and chromatin ??? all the answers on the internet I've found so far have been very confusing. I know it's probably a dumb question but I just dont understand
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macpatgh-Sheldon
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Hi,

Let me try to help you, although your knowledge on this highly detailed topic is probs superior to mine as I am not a cell biologist.

Because the total length of DNA molecules in the nucleus (which in total form the full chromosomal DNA) is much greater than the diameter of the nucleus, the DNA needs to be folded and compacted.

The overall total of folding involves combination of DNA with structural proteins and makes chromatin.

Out of this total folding process there are different levels or a hierarchy. The first level of folding entails the coiling of the DNA double strand around a core of histone (one of the proteins involved in the overall folding), giving rise to a nucleosome - this results in a DNA-protein package that is about 7 times shorter than naked DNA. (there are four types of histones involved: H2A, H2B, H3 and H4.

After that, there are other levels, the 2nd one leading to a "30-nm fibre", which is about 40 times shorter than naked DNA.

In simple terms, the difference between the two is that the nucleosome is a product of the first level of compaction, while the chromatin is the final product.

I hope this makes it easy for you!

M (specialist biology tutor)
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OxFossil
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(Original post by sarah5)
hello
What is the difference between nucleosome,chromosomes and chromatin ??? all the answers on the internet I've found so far have been very confusing. I know it's probably a dumb question but I just dont understand
As macpatelgh says, these are all terms for different levels of organisation of DNA.

Most of the time, the DNA in the nucleus is more or less closely associated with histone proteins. "Chromatin" is the term usually used to refer to this mixture of DNA and histones.

In some stretches, the DNA is tightly coiled around a complex of histone proteins, so that they look like knots on a string. Each "knot" is called a nucleosome.

However, during interphase (i.e. most of the time), not all the chromatin is so tightly organised. Some stretches of the DNA are less tightly coiled around the histones, to allows other proteins and RNA to get access to the DNA so that gene transcription can take place. (DNA in nucleosomes is hard to get at).

The overall appearance of the DNA during interphase is therefore a kind of diffuse, blurry network of chromatin - some of it tightly coiled into nucleosomes, some of it open for transcription.

When cell division is about to take place, the DNA coils tightly around its histones. The diffuse network of chromatin becomes highly "condensed", and we can see it much more easily as it separates out into distinct structures called chromosomes. Each chromosome is a length of tightly coiled chromatin.

After cell division, with gene transcription increasing, the chromosomes "disappear" as the chromatin relaxes into its normal state of mixed open stretches of DNA (where transcription is taking place) and more tightly coiled nucleosomes (where transcription is much reduced).
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sarah5
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thank you so much

(Original post by macpatelgh)
Hi,

Let me try to help you, although your knowledge on this highly detailed topic is probs superior to mine as I am not a cell biologist.

Because the total length of DNA molecules in the nucleus (which in total form the full chromosomal DNA) is much greater than the diameter of the nucleus, the DNA needs to be folded and compacted.

The overall total of folding involves combination of DNA with structural proteins and makes chromatin.

Out of this total folding process there are different levels or a hierarchy. The first level of folding entails the coiling of the DNA double strand around a core of histone (one of the proteins involved in the overall folding), giving rise to a nucleosome - this results in a DNA-protein package that is about 7 times shorter than naked DNA. (there are four types of histones involved: H2A, H2B, H3 and H4.

After that, there are other levels, the 2nd one leading to a "30-nm fibre", which is about 40 times shorter than naked DNA.

In simple terms, the difference between the two is that the nucleosome is a product of the first level of compaction, while the chromatin is the final product.

I hope this makes it easy for you!

M (specialist biology tutor)
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sarah5
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#5
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Yes i got it now thank you so much

(Original post by OxFossil)
As macpatelgh says, these are all terms for different levels of organisation of DNA.

Most of the time, the DNA in the nucleus is more or less closely associated with histone proteins. "Chromatin" is the term usually used to refer to this mixture of DNA and histones.

In some stretches, the DNA is tightly coiled around a complex of histone proteins, so that they look like knots on a string. Each "knot" is called a nucleosome.

However, during interphase (i.e. most of the time), not all the chromatin is so tightly organised. Some stretches of the DNA are less tightly coiled around the histones, to allows other proteins and RNA to get access to the DNA so that gene transcription can take place. (DNA in nucleosomes is hard to get at).

The overall appearance of the DNA during interphase is therefore a kind of diffuse, blurry network of chromatin - some of it tightly coiled into nucleosomes, some of it open for transcription.

When cell division is about to take place, the DNA coils tightly around its histones. The diffuse network of chromatin becomes highly "condensed", and we can see it much more easily as it separates out into distinct structures called chromosomes. Each chromosome is a length of tightly coiled chromatin.

After cell division, with gene transcription increasing, the chromosomes "disappear" as the chromatin relaxes into its normal state of mixed open stretches of DNA (where transcription is taking place) and more tightly coiled nucleosomes (where transcription is much reduced).
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