Describe the three different types of point mutation, and explain for each what the effect on the final gene product is likely to be
- Base insertion/addition. This is when a base pair is added to a sequence - for example AGTCGTAGC could become AGTCGATAGC. In this situation, a frame shift occurs, and every codon downstream of the mutation is translated incorrectly. This is because of the non-overlapping nature of the genetic code. The final protein product will be very different to the original as every amino acid downstream of the mutation is likely to be altered.If a multiple of 3 base pairs is inserted, then the reading frame with remain intact but the final product will be contain one or more extra amino acids.2) Base deletion. This is when a base pair is removed from a sequence - for example AGTCGTAGC could become AGTGTAGC. This has a similar effect to base addition, where the reading frame is altered (frame shift). Every codon downstream of the mutation will be translated incorrectly and the final gene product will be very different to the original. Again, if a multiple of 3 base pairs is deleted, the reading frame will be intact but the final product will be missing one or more amino acids.3) Base substitution. This is when one nucleotide is substituted for different nucleotide - for example AGTCGTAGC could become AGTGGTAGC. This could be a transition (purine-purine or pyrimidine-pyrimidine) or a transversion (purine-pyrimidine or vice versa).There are three possible outcomes for the final product in this situation:there could be no change - the genetic code is degenerate, and as such multiple codons can code for the same amino acid. It is possible that the new codon produced could code for the same amino acid as the original, and therefore have no effect on the final product.there could be a single amino acid change - in this case, the new codon codes for a different amino acid to the old, leading to a small change in the primary structure of the final product.there could be a truncated protein produced - the new codon produced could be a stop codon, meaning that transcription/translation will stop prematurely and a shorter amino acid chain is produced. This truncated protein is very likely to be non-functional.
