biology question

Question

Would the deletion of one nucleotide have more or less of an effect on a protein's function than the deletion of three nucleotides?

a- One nucleotide deletion would have less of an effect because it would only get rid of one amino acid

b- Three nucleotide deletion would have less of an effect because it would only get rid of one amino acid

c- They would both have the same effect

Answer 1

I agree with Heather, deleting one nucleotide would change the codon usage (called frameshift mutation), and a completely different amino acid would result that is incorporated into that part of the peptide chain. Does this change the actual function of the protein? It can or it can do nothing. This depends on where in the nucleotide sequence the nucleotide is missing and how these results into a different amino acid that when now being part of the peptide drastically changes the function of the protein. Nonetheless, because a single nucleotide is going and the amino acid needs 3 that correspond to a particular amino acid, one missing shift the whole reading frame and could very well alter the function of the entire protein.

If 3 nucleotides (that are in a row) are deleted, this could also change the function of the protein, but in this case, it is not as clear, If the 3 nucleotides that are deleted are in frame with the open reading frame of the proteins translation start site, then most likely, the result would be the absence of the amino acid that is coded by the 3 missing nucleotides, and whether or not that has any physiological consequence depends on if that amino acid is critical for the structure of the protein or some other crucial part that is important for its biological activity, then missing those 3 could very well destroy the function of that protein. The question itself is somewhat vague because.it does not tell you anything about reading frames (there are 6, I think), silent mutations, or other genetic mutations that are not as straightforward as they seem. Hope this helps, John

Answer 2

DNA is translated into amino acids by using codons which are three nucleotides. Deleting one nucleotide causes a frame-shift mutation which affects every amino acid downstream (after) of the mutation. Deleting three nucleotides would delete one amino acid but have no affect on the amino acids occurring after it.