Thread: A quick question about mutations

So, we have mutations of the final base pair of a codon. In some cases, altering the last base will have no effect on the amino acid that is coded for. Whereas in other cases, you can mutate the last base of a codon and it will lead to development of a different amino acid.

For example,

I may have CTA mutate to become CTT. In doing such, I have an mrna strand of GAA rather than GAU, which codes for the amino acid GLU rather than ASP.

Is this a true statement? It appears to be, but I have read elsewhere that it is not. So to be safe, I figured id ask here. Maybe I am missing something about this seemingly clear subject.

My second question, it has been some time since my bio classes. Could anyone inform me of the difference between mrna and rrna?

thank you all

What you've written is essentially correct.


The DNA sequence
---CTACTT--- will have an mRNA complement with the sequence
---GAUGAA--- which when translated will result in the amino acids
---Asp-Glu---

Many codons exhibit a third base redundancy. For example, the codons UCU UCC UCA UCG all code for Ser (an example of fourfold redundancy). This degeneracy does not apply to all codons however. For example, the codons UUU and UUC code for Phe while the codons UUA UUG code for Leu. In your example, GAU and GAA code for different amino acids (Asp and Glu, respectively), this being another instance where the last base is not redundant in all cases. Notice however that there is a twofold redundancy here: GAU and GAC code for Asp while GAA and GAG code for Glu.

mRNA (messenger RNA) carries information from the DNA to the protein translation machinery, where it is translated into protein.
rRNA (ribisomal RNA) are the major structural and catalytic components of the ribosome (the site of mRNA translation); they are never translated into protein.

Perfect, thank you.