Ribosomes made in nucleolus, rRNA made in nucleus?

[ipodtouch]

I understand that nucleolus is actually in the nucleus.

Im wondering if rRNA is made where mRNA is transcribed, different area from ribosomal synth.

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[gettheleadout]

rRNA itself is transcribed in the nucleolus, where ribosomes are assembled (from rRNA and ribosomal proteins) in totality. Keep in mind though, that the ribosomal proteins are translated from mRNA outside the nucleus and imported back in before they can be used for ribosome assembly in the nucleolus.

 

[SH3]

I understand that nucleolus is actually in the nucleus.

Im wondering if rRNA is made where mRNA is transcribed, different area from ribosomal synth.

All RNA is produced in the nucleus.

The thing about rRNA is that it is constitutively expressed. The rRNA genes are encoded for multiple times along the length of the genome. This means that it's expressed/being transcribed all the time. Because of this, the area of the genome that encodes the rRNA genes appears as a dark spot because the area is so dense due to the heavy amount of transcription. This essentially produces the Nucleolus.

mRNA isn't constituvely expressed from genes and therefore areas where mRNA is transcribed don't appear as dense.

That's why the nucleolus is located within the nucleus.

 

[ingramw1202]

rRNA itself is transcribed in the nucleolus, where ribosomes are assembled (from rRNA and ribosomal proteins) in totality. Keep in mind though, that the ribosomal proteins are translated from mRNA outside the nucleus and imported back in before they can be used for ribosome assembly in the nucleolus.

beautiful quote