Biology – Mutation and Its Consequences

A mutation involves changes in the base sequences of DNA; an example of this is when a gene is copied incorrectly. The change shifts to make a different amino acid which then codes for a different protein.

One way a gene can mutate in via substitution which is when one of the genes is replaced by a wrong gene. For example the amino acid CGT which normally codes for GCA could change to CGG which then codes for GCC. In most cases then this new code will cause the polypeptide chain to be different due to a change in the primary structure.

Another way a gene can mutate is via addition, this is when a base is added causing what’s called a frame shift as all of the bases are moved along. The final way a mutation can occur is deletion which is when a base is removed rather than inserted and this has the same effect of the sequence. If the addition or deletion occurs towards the end of the sequence the consequences can be minor however effects can be quite significant if it occurs towards the start of the sequence.

There are three effects of a gene mutation. Firstly there is what’s called a nonsense mutation which is when the change in the base sequence causes a stop codon to arise causing the change to end prematurely. This means a protein can be very different and may not function properly. A missense mutation is when the base change causes a change in the code that is translated and then this causes a change in the primary structure due to a different amino acid. This can be quite significant in enzymes as the change in structure causes a change in the active site meaning it cannot turn substrates into products anymore. Finally a silent mutation is when although the base sequence is changed the final protein that is made is no different as the same amino acid is made. The majority of mutations are harmful to people and can causes diseases such as cystic fibrosis.

Gene mutations can sometimes be cause by no environmental factors at all