Gene mutations
What is a gene mutation?
Sudden and spontaneous changes in phenotype, for which there are no conventional genetic explanations or any microscopic evidence of chromosomal mutation, can only be explained in terms of changes in gene structure. A gene mutation or point mutation (since it applies to a particular gene locus) is the result of a change in the nucleotide sequence of the DNA molecule in a particular region of the chromosome. Such a change in the base sequence of the gene is transmitted to mRNA during transcription and may result in a change in the amino acid sequence of the polypeptide chain produced from it during translation at the ribosomes.
Types of gene mutation
There are a variety of forms of gene mutation involving the addition, loss or rearrangement of bases in the gene. These mutations take the form of the duplication, insertion, deletion, inversion or substitution of bases. In all cases they change the nucleotide sequence and result in the formation of a modified polypeptide. For example, deletion causes a frame-shift.