“Redundancy” or “degeneration” of the genetic code occurs during which step of protein synthesis?
A) DNA replication
B) Transcription
C) Post-transcriptional modification
D) Translation
E) Protein glycosylation
The correct answer and explanation is :
The correct answer is:
D) Translation
Explanation:
The genetic code is described as redundant (or degenerate) because multiple codons can code for the same amino acid. This characteristic of the genetic code is particularly relevant during the translation phase of protein synthesis.
Understanding Redundancy in the Genetic Code:
The genetic code consists of 64 codons (triplets of nucleotides) that specify 20 amino acids and stop signals. This means that more than one codon can specify the same amino acid. For example:
- Leucine (Leu) is encoded by six different codons: CUU, CUC, CUA, CUG, UUA, UUG.
- Serine (Ser) is encoded by six codons: UCU, UCC, UCA, UCG, AGU, AGC.
This redundancy helps protect against the effects of point mutations (changes in a single nucleotide). A mutation in the third position of a codon (the wobble position) often does not alter the amino acid sequence, making the genetic code more fault-tolerant.
Why Does Redundancy Occur in Translation?
During translation, tRNA molecules recognize codons on the mRNA through their anticodons and bring the corresponding amino acids. Since multiple codons can correspond to the same amino acid, some tRNA molecules recognize more than one codon, further contributing to the degeneracy of the genetic code.
Why Not the Other Steps?
- A) DNA replication – This is the process of copying DNA before cell division and does not involve codons.
- B) Transcription – This converts DNA into mRNA but does not involve the selection of amino acids.
- C) Post-transcriptional modification – This occurs in eukaryotes (e.g., splicing, polyadenylation) but does not impact codon redundancy.
- E) Protein glycosylation – This is a post-translational modification affecting proteins after translation.
Thus, redundancy of the genetic code primarily affects the translation process.