Bio question--- from qvault

[JustwantDDS]

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Which of the following is not a primary function of nucleosomes located in highly condensed chromatin?
A.
Assist in the efficient storage of genetic material.
B.
Condense genetic material.
C. [Correct]
Expose promoter regions.
D.
Coil DNA.
E.
All of the above options are not primary functions of nucleosomes.

Explanation
Nucleosomes assist in the efficient storage of genetic material through coiling, and thus condensing, DNA. By limiting access to promoter regions within DNA, nucleosomes also play a role in gene regulation.


so nucleosomes do regulate genes by exposing promoter regions, its just not a "primary function" ???

 

[molar3]

hmmmm, well imo since its highly condensed chromatin aka probably heterochromatin, then the promotor regions wouldnt even be being exposed in this case since its tightly wound. that would happen in euchromatic chromatin, where the promotor and other regions would be being exposed
maybe theres a diff /better explanation for this though

 

[LetsGo2DSchool]

There are two types of chromatin: euchromatin and the other one which I can't remember the name. One of them (I forget which one--darn I need to review Bio!) is condensed chromatin while the other is not condensed. The DNA is inactive in the condensed version whereas it's active in the noncondensed version. Thus the nucleosomes located in the condensed version will not expose promoter regions for transcription to occur.

 

[JustwantDDS]

hmm so that explanation is wrong then...
i mean the obvious stick out answer is C which is how i got it correct anyway
i just didnt know if they have a role in regulation at all..........

 

[GeneralChowFun]

Which of the following is not a primary function of nucleosomes located in highly condensed chromatin?
A.
Assist in the efficient storage of genetic material.
B.
Condense genetic material.
C. [Correct]
Expose promoter regions.
D.
Coil DNA.
E.
All of the above options are not primary functions of nucleosomes.

Explanation
Nucleosomes assist in the efficient storage of genetic material through coiling, and thus condensing, DNA. By limiting access to promoter regions within DNA, nucleosomes also play a role in gene regulation.


so nucleosomes do regulate genes by exposing promoter regions, its just not a "primary function" ???

I feel your pain on this one..... Its one of those poorly worded what is the BEST right answer types of questions..... I'll explain:

Nucleosomes in their natural state have promoter regions wrapped around them and inaccessible to RNA Polymerase.
Through histone modification, the DNA becomes "loose" and "unwraps" from the histone/nucleosome complex and the promoter then becomes exposed and available for RNA Polymerase to bind.

The rub here is that the Nucleosome's "job" is to keep the DNA wrapped tight, while is has to be "modified" to stop performing that "job" and allow the promoter to be exposed for transcription to occur.

 

[GeneralChowFun]

There are two types of chromatin: euchromatin and the other one which I can't remember the name. One of them (I forget which one--darn I need to review Bio!) is condensed chromatin while the other is not condensed. The DNA is inactive in the condensed version whereas it's active in the noncondensed version. Thus the nucleosomes located in the condensed version will not expose promoter regions for transcription to occur.

You're thinking of heterchromatin, both types of chromatin are considered "condensed" and wrapped around nucleosomes, heterochromatin can be considered "more" condensed due to the repeat regions and vast A:T rich regions which can pack more tightly.... heterochromatin contains virtually no genes and a high nukmber of repeats whereas the opposite is true of euchromatin...... the density of the chromatin has less to with the presence of genes than the location of the regions on the chromosome. 👍