Questions & Answers

Initiation codon is

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Hint: Let us first understand what is meant by initiation codon. In the process of translation, the messenger RNA (mRNA) transcript has the start codon known as initiation codon that is translated by ribosomes.

Complete answer:
Translation is a process in which the messenger RNA (mRNA)molecule that contains the genetic code is decoded in order to form a specific sequence of amino acids in a polypeptide chain.

In Archaea and N formylmethionine in bacteria, in eukaryotes, plastids and mitochondria. AUG is considered as the initiation codon that always codes for methionine. The initiation codon is usually preceded by 5’ UTR (5’ untranslated region). The ribosome binding site is also included in this in prokaryotes. The stop codons are the nonsense codons that do not code for any amino acids. Their presence indicates the termination of translation. The stop codons for mRNA translation are UGA, UAG, UAA.

Additional information:
The tRNA has the anticodons that matches perfectly with the codon of mRNA and codes for a specific amino acid of that tRNA.
>UUU is the mRNA codon that codes for the amino acid phenylalanine. It is bound by the anticodon AAA.
>UGA and UAG are the stop codons that are used to indicate the termination of the translation process and do not code for any amino acid. They are also known as nonsense codons.

Therefore the correct answer is option (D) AUG.

Note: There are alternative start codons in both eukaryotes and prokaryotes that are different from standard initiation codon AUG. These alternate codons are still translated as methionine (Met) when they are present at the start of the protein. This is because for initiation, a distinct transfer RNA (tRNA) is used. Prokaryotes mainly use UUG and GUG alternative initiation codons.