If one nucleotide was substituted within a gene what would happen to the structure of the gene?

Question

Basically if one nucleotide was substituted within a gene what would most likely affect the structure of the protein coded for by that gene.

Answer 1

The potential effects range from no change to loss of the protein depending on where the mutation occurs. If the mutation happened in an intron or in the 5' or 3' UTR, then most likely nothing would happen.

If the mutation is in the coding region of the gene, then several things could happen. A mutation creating a stop codon will cause premature termination protein synthesis. Because there are 64 possible codons for 20 amino acids, most amino acids have multiple codons, from 6 (leucine and arginine) to 1 (methionine and tryptophan). The third position of the codon is most permissive towards mutations. Often, a change in the 3rd position of a codon will encode for the same or similar protein such as Asn for Lys or Asp for Glu.

But, 2 out of 3 times, the mutation will be in the first or second position which usually results in a more significant change such as polar for hydrophobic, charged to uncharged, thiol or hydroxyl to alkly residue. These types of mutations can often result in a change in structure.

There are some more exotic possibilities. A premature stop codon can lead to loss of the protein through nonsense mediated decay of the mRNA. Some amino acids are sites of post-translational modification so mutations there can result in the loss or creation of sites for glycosylation, lipid modification, phosphorylation or hydroxylation.

A silent mutation, where the new codon is assigned to the same amino acid, can have serious consequences. For example, a silent mutation in exon 7 of SMN2 alters a splicing signal that causes skipping of exon 7. The mutant protein is unstable and is rapidly degraded. Other genes with mutations in splicing signals include BRCA1 and CFTA.

The answer you need depends on how advanced your course is.

Answer 2

it would depend whether the substitution is silent (no change in the amino acid), nonsense mutation (that creates a stop codon, where the translation of mRNA would stop truncating the protein) or just a simple missense mutation that would change the amino acid. Depending on the nature of the amino acid change a number of effects can happen - from nothing if the new amino acid is similar in it's properties to the one that was replaced, to a completely different structure by disrupting H-bonds, ionic interactions, changing the secondary structure from an alpha helix or beta sheet to a loop or may result in improper folding of the protein (proline will change the kink of the protein, lysine, arginine are positively charged, aspartate and glutamate are negatively charged etc.)

Answer 3

most likely nothing would happen.

each sequence of three nucleotides (codons) codes for a particular amino acid in the protein. there are 64 codons but only 20 amino acids, each amino acid is coded for by 2-4 different codons, so there's a good chance that nucleotide substitution will result in no change to the protein. furthermore, substitutions tend to change the resulting amino acid to a chemically similar amino acid, so that the effect on structure is slight. lastly, proteins consist of hundreds or thousands of amino acids, but only a few dozen structural elements that determine their shape - most amino acid substitutions don't change the protein's shape very much.

Answer 4

Gene Hackman

Answer 5

The code for aminoacids, is made in triplets, in such a manner, that three bases will have the code for a single aminoacid,,,
Since this code by definition is "degenerated", the substitution of A SINGLE nucleotide, if it makes it to the ribosome,,,,NOTHING will happen.,,
You need only one pair of basis to be correct in that aminoacid...for example GCA- GCU- GCC all three of them will codify alanine,,,,it does not matter if the lst of the basis is not the same.......
The questio refers that" the code for the 20 aminoacids is degenerate", applies very well to this example..
The substitution of ONE single nucleotide in the triplet, WILL NOT change the aminoacid...the sequence will be the same

Answer 6

Several things...
Hydrogen bonding between side chains, Van der Waals interactions, maybe even disulfide bonds with the right amino acids.

Answer 7

I was gonna tell you but Chris said everything i was gonna say, and its much easier to give him props than to retype everything.

Answer 8

mutational changes that may be dangerous and may cause death