Question

Starting codon is universal which means

• A. It is the universally same for all organisms
• B. Two or more codons
• C. Any variable code is called starting codon which can start protein synthesis
• D. All codons originated from same starting codon

Answer 1

The correct option is A It is the universally same for all organisms

The triplet "AUG" codes for methionine and serves as start codon which means that the first codon in almost all reading frames is "AUG". Despite modification in encoded amino acid (methionine in eukaryotes and formyl methionine in prokaryotes), the same codon serves as initiation codon in all the cells of nearly all organisms. Option A is correct. Universality does not mean presence of two or more codons as initiation codon; neither protein synthesis can start randomly at any variable code. Codons are different possible independent combinations of four nucleotide bases; they are not originated from start codon.