Question

Given below are two statements, one is labelled as Assertion (A) and other labelled as Reason (R). 
• [Assertion (A):] The genetic code is degenerative. 
• [Reason (R):] The genetic code is nearly universal. In light of the above statements, choose the correct answer from the options given below. 
 

• A. Both (A) and (R) are true and (R) is the correct explanation of (A).
• B. Both (A) and (R) are true but (R) is NOT the correct explanation of (A).
• C. (A) is true but (R) is false.
• D. (A) is false but (R) is true.

Hint:

To remember key properties of the genetic code:
- Degeneracy: Redundancy (multiple codons, one amino acid).
- Non-ambiguity: Specificity (one codon always codes for only one amino acid).
- Universality: Commonality (same codons across all organisms).

Answer 1

The Correct Option is B

Step 1: Understanding the Concept:
The genetic code is the set of rules by which information encoded within genomic DNA or mRNA transcripts is translated into proteins by living cells.
This code displays several distinct physical and evolutionary properties.

Step 3: Detailed Explanation:
Let us evaluate the Assertion and Reason statements:
- Assertion (A) is true: The genetic code is redundant, or degenerate.
There are 64 possible triplet codons, but only 20 standard amino acids are used to build proteins.
Three codons serve as stop signals, leaving 61 codons to specify 20 amino acids.
Because of this excess, many amino acids are encoded by more than one codon.
For example, the amino acid Leucine is specified by six different codons (UUA, UUG, CUU, CUC, CUA, and CUG).
- Reason (R) is true: The genetic code is nearly universal.
With a few minor exceptions (such as in mitochondria, chloroplasts, and some ciliates), the same codons specify the same amino acids across all domains of life, from bacteria to humans.
This universality is strong evidence of a common evolutionary origin for all life on Earth.
- Evaluating the connection: While both statements are fundamental truths of genetics, they describe independent properties of the genetic code.
Universality (which relates to evolutionary conservation across species) does not explain degeneracy (which refers to redundancy within the code).
Therefore, both statements are true, but (R) is not the correct explanation of (A).

Step 4: Final Answer:
Both (A) and (R) are true, but (R) is not the correct explanation of (A), matching Option (B).