The DNA acts as the organism’s instruction manual, encoding the information needed for protein synthesis (translation) and the regulation of cellular functions. However, this code can undergo alterations, known as mutations, which vary in their impact: from being clinically silent to triggering serious diseases. Discover the main types of genetic mutations and their functional relevance.
1. Synonymous mutation
It is a nucleotide substitution that does not change the encoded amino acid due to the redundancy of the genetic code, keeping the protein sequence unchanged. This occurs because some amino acids are encoded by different combinations of three nucleotides.
Although the majority of synonymous mutations are silent and do not cause any type of pathology, not all synonymous mutations go unnoticed. In some cases, they can affect protein folding or the translation process itself, resulting in diseases such as certain types of cancer.
2. Missense mutation
This type of mutation involves the substitution of a nucleotide that changes the codon and, therefore, the resulting amino acid in the protein. The functionality of the protein will depend on the nature of the new amino acid. It can range from a neutral effect to causing hereditary diseases such as sickle cell anemia.
3. Nonsense mutations
In this case, a codon that originally encoded an amino acid is replaced by a stop codon, leading to a truncated protein (incomplete). The resulting proteins are usually non-functional. This type of mutation is associated with diseases such as Duchenne muscular dystrophy.
4. Frameshift mutation
It occurs when nucleotides are inserted or deleted in a number that is not a multiple of three, which shifts the mRNA reading frame. This results in aberrant proteins with incorrect amino acid sequences and usually a premature stop codon. This type of mutation often has devastating effects on protein function, causing diseases such as cystic fibrosis.
5. Repeat expansion mutations
Some regions of DNA contain short repetitive sequences (such as triplets), which can abnormally expand during replication. Excessive expansion of these repeats can interfere with gene expression or protein structure. A classic example is Huntington’s disease.
6. Structural mutations
At a large scale, chromosomal rearrangements can occur, such as duplications, deletions, inversions, and translocations. These alterations affect extensive segments of the genome and can disrupt multiple genes simultaneously. They are common in cancers, genomic rearrangement syndromes, and various developmental disorders.
