Universality Means Shared Genetic Code Across Life

Steps:

• Recall that the genetic code translates DNA/RNA into proteins using codons for amino acids.
• Define "universal" in biology as a feature common to nearly all organisms, indicating shared evolutionary origin.
• Evaluate choices: A describes codon structure, B redundancy, C mutation effects, D sameness across organisms.
• Select D as it directly matches the definition of universality.

Why D is correct:

• By definition, the genetic code is universal because the same 64 codons specify the same 20 amino acids and stop signals in bacteria, plants, animals, and most other organisms, reflecting a common ancestry.

Why the others are wrong:

• A: Describes triplet codon composition, not universality.
• B: Refers to code degeneracy, where multiple codons code for one amino acid, but not shared across species.
• C: Mutations alter specific genes but do not change the overall code's universality in organisms.

Final answer: D