Question

Some base substitutions do not result in change in amino acid sequence of the polypeptide because

• A. Universality of the codon
• B. triplet nature of codon
• C. Co- linearity
• D. Degeneracy of genetic codon

Hint:

The degeneracy of the genetic code is explained by Francis Crick's Wobble Hypothesis, which states that steric restrictions at the third position of the codon-anticodon interaction are less strict, allowing for non-standard base pairing.

Answer 1

The Correct Option is D

Step 1: Understanding the Concept:
The genetic code consists of three-nucleotide sequences called codons that specify the addition of particular amino acids during protein synthesis.
Because there are 64 possible triplet codons and only 20 standard amino acids, multiple codons can code for the same amino acid.

Step 2: Detailed Explanation:
Let us analyze the terms provided in the options:
1. Degeneracy of the genetic code: This property means that more than one codon can specify a single amino acid.
For example, the amino acid alanine is specified by four different codons: 5'-GCU-3', 5'-GCC-3', 5'-GCA-3', and 5'-GCG-3'.
If a point mutation changes the terminal nucleotide of an alanine codon from U to C (a base substitution), the mutated codon (5'-GCC-3') still codes for alanine.
This is called a silent mutation because the amino acid sequence of the resulting polypeptide remains unchanged.
Therefore, degeneracy is the reason why some base substitutions do not alter the polypeptide sequence.
Let us review the other terms:
- Universality: This means that the same genetic code is shared by almost all living organisms, from bacteria to humans.
- Triplet nature: This means that each codon is composed of three consecutive nucleotide bases.
- Co-linearity: This means that the linear sequence of codons in a gene directly corresponds to the linear sequence of amino acids in the translated polypeptide.

Step 3: Final Answer:
The property that prevents some base substitutions from changing the amino acid sequence is the degeneracy of the genetic codon, which corresponds to option (D).