Let us look at some of these single nucleotide
mutations. They can manifest themselves in
a number of different ways. The first option
is that absolutely nothing changes. It is
not even in a coding region, so it doesn't
matter. But if you were in a coding region,
then a number of things could happen.
First of all, let us look at a silent mutation.
In a silent mutation, we have a one base change
that does not result in any change of amino
acid. You will recall there is
some redundancy in the genetic code, so we're
still coding for prolene and everything is
okay. That mutation is silent. But if we have
a base change in which we start coding for
a different amino acid, we'll result in a missense
mutation. This one we had in the second position
of the triplet code, we definitely are causing
a different amino acid to be added to the
chain and this may or may not have a large
effect depending on whether it is still a
polar amino acid or nonpolar amino acid whether
it has an impact on protein folding.
The final thing is what if we have a base
substitution that results in a stop codon.
Clearly we then have a truncated polypeptide
chain, which is likely to not be functional.
A nonsense mutation means that it creates
a whole bunch of nonsense and it is not a
functional protein. That is just looking at