emäsmuutos

Emäsmuutos, also known as base change or point mutation, is a type of genetic mutation where a single nucleotide base in a DNA sequence is replaced by another. This alteration can occur spontaneously during DNA replication or be induced by external factors like radiation or certain chemicals. The three main types of base changes are transitions, transversions, and insertions/deletions (though the latter is technically not a base *change* but a modification of the sequence).

A transition involves the substitution of a purine (adenine or guanine) with another purine, or a pyrimidine (cytosine or thymine) with another pyrimidine. For example, an adenine might be replaced by a guanine, or a cytosine by a thymine. A transversion, on the other hand, involves the substitution of a purine with a pyrimidine, or vice versa. An example would be an adenine being replaced by a cytosine.

The consequences of an emäsmuutos depend on its location within the gene and the resulting effect on the encoded protein. If the mutation occurs in a non-coding region, it may have no observable effect. However, if it occurs within a gene, it can lead to several outcomes. A silent mutation results in a codon that codes for the same amino acid, thus having no effect on the protein sequence. A missense mutation changes the codon to one that codes for a different amino acid, potentially altering the protein's structure and function. A nonsense mutation transforms a regular codon into a stop codon, prematurely terminating protein synthesis and usually resulting in a non-functional protein. Emäsmuutos is a fundamental concept in genetics and molecular biology, playing a role in evolution, disease, and genetic variation.