Emäsmuutoksia

Emäsmuutoksia, or base changes, refer to modifications in the nucleotide sequence of DNA or RNA where one base is substituted for another. These changes are a fundamental source of genetic variation. In DNA, the four bases are adenine (A), guanine (G), cytosine (C), and thymine (T). An emäsmuutos can occur when, for example, an adenine is replaced by a guanine.

These substitutions can be categorized based on the type of base involved. A purine base (A or G) can be replaced by another purine (a transition), or by a pyrimidine base (C or T) (a transversion). Similarly, a pyrimidine can be replaced by another pyrimidine (transition) or by a purine (transversion). Transitions are generally more common in DNA than transversions due to the similar chemical structures of purines and pyrimidines.

The consequences of an emäsmuutos depend on where it occurs in the genetic material. If the change occurs in a non-coding region, it may have no observable effect. However, if it occurs within a gene, it can alter the resulting protein. A silent mutation results in a codon that codes for the same amino acid, thus having no effect on the protein. A missense mutation leads to a different amino acid being incorporated, potentially changing the protein's function. A nonsense mutation creates a premature stop codon, leading to a truncated and usually non-functional protein. Emäsmuutoksia can arise spontaneously due to errors during DNA replication or be induced by environmental mutagens.