Nonsense mutation

In genetics, a point-nonsense mutation is a point mutation in a sequence of DNA that results in a premature stop codon, or a point-nonsense codon in the transcribed mRNA, and in a truncated, incomplete, and usually nonfunctional protein product. The functional effect of a point-nonsense mutation depends on the location of the stop codon within the coding DNA. For example, the effect of a point-nonsense mutation depends on the proximity of the point-nonsense mutation to the original stop codon, and the degree to which functional subdomains of the protein are affected. A point-nonsense mutation differs from a missense mutation, which is a point mutation where a single nucleotide is changed to cause substitution of a different amino acid. Some genetic disorders, such as thalassemia and DMD, result from point-nonsense mutations. In genetics, a point-nonsense mutation is a point mutation in a sequence of DNA that results in a premature stop codon, or a point-nonsense codon in the transcribed mRNA, and in a truncated, incomplete, and usually nonfunctional protein product. The functional effect of a point-nonsense mutation depends on the location of the stop codon within the coding DNA. For example, the effect of a point-nonsense mutation depends on the proximity of the point-nonsense mutation to the original stop codon, and the degree to which functional subdomains of the protein are affected. A point-nonsense mutation differs from a missense mutation, which is a point mutation where a single nucleotide is changed to cause substitution of a different amino acid. Some genetic disorders, such as thalassemia and DMD, result from point-nonsense mutations. Suppose that a point-nonsense mutation was introduced at the fourth triplet in the DNA sequence (CGA) causing the cytosine to be replaced with thymine, yielding TGA in the DNA sequence. Since TGA is transcribed-then-translated as UGA, the resulting transcript and protein product would be: