Why Does the Genome Have More rRNA Gene Copies Than Ribosomal Protein Genes?

[whamola411]

A eukaryotic ribosome has 4 different rRNA molecules and about 82 different proteins. There is a single copy of the gene for each of the proteins; however there are multiple copies of each rRNA gene. Why does the genome contain more copies of each rRNA gene than for each ribosomal protein gene?



My thinking is that there needs to be so many rRNA gene copies to keep up with the extremely offset ratio of protein:rRNA. I feel like there has to be a better answer though. Thanks!

 

[Ygggdrasil]

If you create one molecule of mRNA for one of the ribosomal proteins, how many ribosomal proteins would you produce. One? More than one? Less than one?

 

[whamola411]

I'm really not sure. I would think none because the ribosomes, and thus their rRNA are recycled after translation.

 

[Ygggdrasil]

In general, a single mRNA molecule will get read by multiple ribosomes creating multiple proteins.

 

[whamola411]

I understand that, but each of those ribosomes is made up of rRNA and proteins. So why would you need more copies of the rRNA than protein?

 

[Ygggdrasil]

How many rRNA molecules will you get if you have RNA polymerase transcribe one rRNA gene?

 

[whamola411]

One.

 

[Ygggdrasil]

So since transcription of the gene for a ribosomal protein results in multiple copies of the protein molecule while transcription of the gene for an rRNA results in only one copy of the rRNA molecule, do you now see why you need multiple copies of the rRNA genes?

 

[whamola411]

Is it because in order to form many ribosomes, there will need to be a high number of rRNA, in addition to the high number of proteins produced?