Need help on mutations in DNA...?

Question

How does it affect RNA and a protein?

What are some control mechanisms?

Answer 1

If there is a mistake in the DNA sequence, it will be transcribed into the mRNA molecule that is created from the template. The mRNA will then be fed through a ribosome and translated into a protein. However, if there is now a mistake in the mRNA, there will be a corresponding mistake in the protein. There are a couple different types of mistakes that can be made - if there is an insertion or deletion of a base in the DNA/RNA, the reading frame is shifted, and sometimes that causes the protein to be prematurely cut off, etc. If one base is swapped for another, that can cause the wrong amino acid to be inserted into the protein. (if you're lucky, sometimes this swap won't affect which amino acid gets inserted. That's called a "silent mutation.") In general, a mistake in DNA leads to a mistake in RNA, which leads to the wrong protein/a faulty protein being produced.

The one control mechanism that I can remember is coded into the DNA itself - if the reading frame is shifted, then the translation mechanism will hit a stop codon very early on in the translation, meaning that instead of producing a faulty protein (which could function in such a way that it actually damages a cell) you don't produce the protein at all. I think there are also elements that "proofread" the DNA strand ahead of the replication fork, but I'm not entirely sure of the mechanism behind that. Hope this helps...good luck!