True about genetic code except
**Core Concept**
The genetic code is a set of rules used by living cells to translate information encoded within genetic material (DNA or RNA) into proteins. This code consists of a sequence of nucleotides that specify the amino acid sequence of a protein.
**Why the Correct Answer is Right**
The genetic code is nearly universal, meaning that almost all living organisms use the same code to translate DNA or RNA into proteins. This universality is due to the fact that the genetic code is based on the chemical properties of the nucleotides and the amino acids, which are conserved across different species. The code is read in a triplet fashion, with each triplet of nucleotides (codon) specifying one of the 20 amino acids. The sequence of codons in a gene determines the amino acid sequence of the protein.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect because the genetic code is not entirely degenerate. Degeneracy refers to the fact that multiple codons can encode the same amino acid. However, not all amino acids have multiple codons.
**Option B:** This option is incorrect because the genetic code is not context-dependent. The sequence of codons in a gene determines the amino acid sequence of the protein, regardless of the surrounding sequence.
**Option C:** This option is incorrect because the genetic code is not ambiguous. Each codon specifies one of the 20 amino acids, and there are no ambiguous codons that could be interpreted in multiple ways.
**Clinical Pearl / High-Yield Fact**
It's essential to remember that the genetic code is nearly universal, but there are a few exceptions, such as in mitochondria, where a different codon is used to specify the amino acid methionine. This is known as the "mitochondrial genetic code."
**Correct Answer: D**