Provide an explanation on how is it possible that two mRNA segments with some differences with their polynucleotide sequence give simillar polypeptide
The Correct Answer and Explanation is:
The possibility of two mRNA segments with different polynucleotide sequences resulting in similar polypeptides is due to the redundancy and flexibility of the genetic code. The genetic code is made up of triplets of nucleotides, called codons, which each correspond to a specific amino acid or a stop signal during protein synthesis. However, there are 64 possible codons (4^3 combinations of nucleotides) but only 20 amino acids, meaning some amino acids are encoded by more than one codon. This is known as codon redundancy or degeneracy.
For example, the amino acid leucine is encoded by six different codons, such as UUA, UUG, CUU, CUC, CUA, and CUG. This redundancy means that small changes in the nucleotide sequence of the mRNA may not affect the amino acid sequence of the resulting protein. This is especially true if the change occurs in the third position of the codon (known as the wobble position), where substitutions often don’t alter the encoded amino acid due to the flexibility of base pairing.
Furthermore, some mutations in the mRNA can lead to synonymous substitutions, where a nucleotide change does not result in a different amino acid being incorporated into the polypeptide. These synonymous changes occur because the new codon still codes for the same amino acid due to the redundancy in the genetic code.
In addition, protein folding and function can sometimes tolerate certain changes in sequence without significantly altering the protein’s structure or activity. This is because proteins are complex structures, and the overall function can sometimes be maintained even with minor variations in the sequence, particularly if the changed residue is not in a critical region of the protein.
Thus, even with differences in the nucleotide sequence, similar polypeptides can still be produced due to the redundancy of the genetic code and the tolerance of the protein structure to small variations.
