Mutation

Mutations are alterations in the DNA sequence that can happen spontaneously during DNA replication or be triggered by mutagenic factors such as ionizing radiation (gamma rays, UV radiation) and harmful chemicals (toxins found in cigarette smoke). These changes can impact the proteins encoded by genes, leading to different effects on the cell depending on the type of mutation. There are three primary types of gene mutations:

1. nucleotide substitution

One nucleotide is swapped for a different one. This may have little or no impact if the new codon still specifies the same amino acid (silent mutation). However, if it results in a different amino acid, it could cause a slight alteration in the protein’s function.

2. nucleotide  insertion

Extra nucleotides are introduced into the sequence, shifting how the genetic code is read.

3. nucleotide deletion

One or more nucleotides are removed from the sequence.

Frameshift mutations (insertions and deletions) generally have more serious effects than substitutions because they disrupt the reading frame of the entire sequence.

Example of a frameshift mutation caused by nucleotide deletion

These mutations may also create a premature STOP signal, resulting in an incomplete and nonfunctional protein. While many mutations are detrimental, some have no effect, and a few may even be advantageous. Mutations contribute to genetic diversity, which can drive evolutionary change by introducing new traits into a population.

In summary, most mutations that affect the function of the cell will bring this change about by causing the changes in the sequence.