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 the same starting codon

Answer 1

Hint: A codon is a three-nucleotide sequence of DNA or RNA that corresponds to a specific amino acid or stop signal during protein synthesis. DNA and RNA molecules are written in a four-nucleotide language, whereas proteins are written in a 20-amino acid language.

Complete answer:
The start codon is the first codon of a messenger RNA (mRNA) transcript that a ribosome will translate. In eukaryotes and Archaea, the start codon always codes for methionine, while in bacteria, mitochondria, and plastids, it codes for N-formylmethionine (fMet). AUG is the most commonly used start codon (i.e., ATG in the corresponding DNA sequence).
A 5' untranslated region (5' UTR) is frequently present before the start codon. This includes the ribosome binding site in prokaryotes.
The triplet "AUG '' codes for methionine and serves as the start codon, so "AUG" is the first codon in almost all reading frames. Despite changes in the encoded amino acid (methionine in eukaryotes and formylmethionine in prokaryotes), the same codon serves as the initiation codon in nearly all cells.
The presence of two or more codons as initiation codons does not imply universality; protein synthesis can begin at any variable code. Codons are distinct independent combinations of four nucleotide bases that do not originate from the start codon.

Thus, the answer is option A: It is the universally same for all organisms

Note:
Alternative start codons are found in both prokaryotes (bacteria and archaea) and eukaryotes and differ from the standard AUG codon. When alternate start codons occur at the beginning of a protein, they are still translated as Met (even if the codon encodes a different amino acid otherwise). This is due to the use of a separate transfer RNA (tRNA) for initiation