Question

1. Using the following mRNA sequence, AUG GUG CCA UUC AAU AUG UGG provide a definition and an example of each of the following mutations: silent, nonsense, missense, and frameshift mutation. please explain using the sequence for me to understand.

Answer 1

AUG GUG CCA UUC AAU AUG UGG

( you need a start codon followed by coding sequence and a stop codon in the mRNA sequence for explaining the terms)

So consider the mRNA sequence- AUG GUG CCA UUC AAU UGA UGG

1. Silent mutation

As the name suggests, silent mutations are silent, they do not show any effect on an organism's phenotype. We know that amino acids can be coded by more than one codon. For ex- proline has CCU, CCC, CCA, CCG- all these four codons code for one amino acid- proline.

AUG GUG CCA UUC AAU UGA UGG

Start codon- val- pro -phe -asn -stop codon

Silent mutation results in

AUG GUG CCG UUC AAU UGA UGG

Start codon- val- pro- phe- asn- stop codon

We can see that there is no changes after translation.

Nonsense mutation

In a nonsense mutation, one of the codons in the coding region codes for a stop codon which results into a non functional protein.

Example

AUG GUG CCA UAG AAU UGA UGG

UAG- stop codon in between leads to non functional protein

3, Missense mutation

It is a mutation where a single nucletoide difference leads to change in the amino acid. It is opposite to silent mutation

AUG GUG CAA UUC AAU UGA UGG

Here instead of CCA, the codon has changed to CAA, changing proline to glutamine

4, Frameshift mutation

The addition or deletion of basepairs in the DNA results in frameshift change. It results in completely different of amino acids after translation when compared to the original one

Example

TAC CAC GGT AAG TTA ACT

AUG GUG CCA UUC AAU UGA

By frameshift mutation,

TAC CAC GGT AA TTA ACT

AUG GUG CCA UUA AUU GA--- CONTINUES

we can see the triplet codon completely changes when one base pair in DNA is deleted.