Final answer:
The protein truncation test is designed to detect nonsense mutations, which create a premature stop codon in the DNA sequence that leads to truncated, usually nonfunctional proteins. It is not used for detecting missense, frameshift, or silent mutations, which do not always result in a truncated protein. The correct answer is option 2.
Step-by-step explanation:
Types of Mutations Detected by the Protein Truncation Test
The protein truncation test is specifically designed to detect nonsense mutations in genes. A nonsense mutation occurs when a point mutation causes a normal codon to become a stop codon, resulting in the premature termination of protein synthesis. This leads to a truncated protein product, often rendering it nonfunctional. Unlike silent mutations, which do not alter the amino acid sequence, or missense mutations, which substitute one amino acid for another, nonsense mutations introduce a stop signal that halts the protein-building process. Protein truncation tests are therefore not used to identify missense or silent mutations as they don't result in truncated proteins.
A frameshift mutation also results in a change in the reading frame of the genetic sequence, but this type of mutation is caused by insertions or deletions of bases that are not in multiples of three, thereby altering the entire downstream amino acid sequence. While frameshift mutations often result in nonfunctional proteins, the detection of these by protein truncation test may not be as straightforward as the direct impact of nonsense mutations.