Insertion errors: If an extra nucleotide (base) is inserted into the mRNA during transcription, the reading frame of the mRNA is shifted. This leads to a frameshift mutation, where all the codons downstream of the insertion are read differently, causing the protein to be produced incorrectly or even rendered non-functional.
Deletion errors: Conversely, if a nucleotide is deleted during transcription, the reading frame is also altered, leading to a frameshift mutation. The protein will have an incorrect sequence and structure from the point of deletion onward, compromising its function.
Substitution errors: These occur when one nucleotide is mistakenly inserted in place of another. Substitution errors can have varying effects on the protein depending on the specific nucleotide change. Some changes may lead to the incorporation of a different amino acid into the protein, altering its structure and potentially affecting its function. Other substitution errors might not change the resulting amino acid, thus retaining the original function.
Nonsense mutations: These occur when a transcription error results in the insertion of a premature stop codon into the mRNA sequence. Stop codons normally signal the end of protein synthesis, so their introduction leads to the production of a truncated protein that lacks the essential parts needed for proper function.
Missense mutations: These types of errors result in the incorporation of a different amino acid into the protein due to a change in the codon. Depending on the nature of the new amino acid and its position in the protein, this change could alter the structure and function of the protein or even render it inactive.
Silent mutations: In certain cases, transcription errors may not result in any change in the protein sequence. This is because some codons are synonymous and can code for the same amino acid. Changes in these codons during transcription will not affect the protein's structure or function and are referred to as silent mutations.
Overall, errors during transcription have significant consequences for the protein that is produced. They can lead to changes in the protein's structure, function, or even its complete inactivation, depending on the specific nature and location of the mistake made during the transcription process.
