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The simplest type of mutation happens when one DNA letter, called a nucleotide, is replaced by another. This type of change is known as a point mutation or a single nucleotide variant (SNV) (Alberts et al., 2015).

If a point mutation is passed from parents to children and becomes common in a population, it is called a single nucleotide polymorphism (SNP). A change is usually considered an SNP only if it appears in at least a small part of the population, for example in about 1% of people (Griffiths et al., 2019).

For example, imagine that 98% of people have the DNA sequence:

…acgtgcgAtgattg…

but 2% of people have a slightly different version:

…acgtgcgTtgattg…

In this case, the DNA letter A is replaced by T at one position. This is an example of an A-to-T SNP.

If this SNP is located inside a gene, it is called an allele or gene variant. Different alleles can lead to small differences between individuals, such as eye color, height, or the ability to digest certain foods (Strachan & Read, 2018).

Most point mutations have no visible effect, but some can change how a protein works or how much of it is produced. In certain cases, point mutations are linked to genetic diseases, while in other cases they simply increase genetic diversity in a population (National Human Genome Research Institute, 2023).