Variation and Evolution: Mutations

A mutation refers to a change in the genetic material - whether in the entire genome of an organism or in a single DNA building block (nucleotide).
Mutations can occur randomly and spontaneously during DNA replication. They can also be triggered by environmental factors including radiation and chemicals.
A majority of mutations are neutral, meaning they do not affect an organism’s phenotype (the set of observable characteristics). However, some cause changes in physical traits, which can have positive, negative, or neutral effects.
If a mutation happens in a body (somatic) cell, it can lead to a cell growing and dividing uncontrollably, which can result in cancer.
If a mutation occurs in a sex cell (like egg or sperm), it can be passed on to future generations. This is how new alleles - versions of genes - can be introduced into a population.
Mutation plays a crucial part in evolution because it increases genetic variation. Since the environment changes over time, certain mutations may better equip an organism to survive and reproduce. This is known as natural selection or ‘survival of the fittest’.
Genetic variation brought about by mutation is the raw material upon which natural selection operates. Without variation, there would not be the differential survival and reproduction that is the basis of natural selection.
Many mutations have no discernible effect on the functioning of the organism in which they occur. These are termed ‘silent’ mutations.
Not all mutations are bad. Some can provide advantages to organisms, like resistance to diseases.
The rate at which mutation occurs can be influenced by several factors. Some of these include age, sex, and environment.
Some mutations may cause genetic disorders such as cystic fibrosis and sickle cell anaemia. These are often the result of mutations in single genes. Other disorders, like heart disease, are more complex, and involve mutations in multiple genes.
There are different types of mutations: point mutations (affect only one or very few base pairs at a time) and chromosomal mutations (affect the structure of a chromosome).
The study of mutations is of significant importance in understanding and potentially curing several diseases. It is also useful in improving crop varieties and domesticated animals.