Nonsenssimutaatiot

Nonsenssimutaatiot, also known as nonsense mutations, are a type of point mutation that results in the premature termination of protein synthesis. This occurs when a normal codon, which specifies an amino acid, is altered into a stop codon. Stop codons signal the ribosome to terminate translation, leading to the production of a truncated protein. These truncated proteins are often non-functional or have severely impaired function because they lack essential domains or active sites.

The genetic code consists of codons, which are sequences of three nucleotides that dictate the incorporation of a specific amino acid into a growing polypeptide chain. There are 64 possible codons, with 61 specifying amino acids and three acting as stop codons (UAA, UAG, and UGA). Nonsense mutations occur when a single nucleotide change converts a sense codon (one that codes for an amino acid) into one of these three stop codons.

The consequences of a nonsense mutation depend on several factors, including the location of the mutation within the gene. If the mutation occurs early in the coding sequence, the resulting truncated protein will be significantly shorter and likely non-functional. Mutations occurring later in the gene might produce a protein that retains some function, though this is less common. Additionally, cells have mechanisms, such as nonsense-mediated mRNA decay (NMD), that can degrade mRNA containing premature stop codons, further preventing the synthesis of aberrant proteins.

Nonsense mutations are implicated in a variety of genetic disorders, including cystic fibrosis, Duchenne muscular dystrophy, and some forms of cancer. The study of nonsense mutations is crucial for understanding gene function and developing therapeutic strategies for genetic diseases.