Mutations

ID #1240

I was just curious, I know you said that a mutation or mistake in RNA during transcription is not a big deal because even if it is passed on it will be degraded quickly, but what if there was an error in the RNA that is incorporated into a ribosome in an egg cell, will that mutation still have an effect if that egg becomes fertilized?


I love how you're thinking about the next logical step here. This is a great question, but let's examine why this still isn't really that big a deal.

First, it's great that you realize that a mistake could also be made in the transcription of a rRNA molecule, not just an mRNA molecule. But let's remember that just as with errors in transcription of mRNAs, we are assuming that no change has been made to the genome, so the blueprints are still "good." So if you make an error in a rRNA molecule, the next time you transcribe that same gene, you're unlikely to make the same mistake in the same place. And recall just how much transcription is going on of your rRNA genes (those 45S pre-rRNA genes and 5S genes). LOTS! So it is absolutely true that if you make a bad RNA molecule that gets incorporated into a ribosomal subunit, the entire subunit could be defective. But it's also true that the cell in question (egg cell or otherwise) has millions of ribosomal subunits in it! So the truth is having one bad one will go unnoticed, even if it hangs out in the cell for a while.

Oh, and by the way...

Cells are quite good at recognizing when "someone" isn't "pulling their own weight." (I can't seem to keep myself from personifying molecules) So I strongly suspect, although I can't back it up with specific facts without doing a little digging, that a faulty ribosomal subunit would be identified as not doing its job properly, and targeted for destruction. This would certainly cut down on the heredity of a "bad" ribosome from parent cell to daughter cell.

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