During the initiation stage of translation, which molecules must assemble to form the initiation complex?

• A. DNA, RNA polymerase, and ribosomes
• B. mRNA, DNA polymerase, and tRNA
• C. mRNA, small ribosomal subunit, initiator tRNA, and large ribosomal subunit
• D. Large ribosomal subunit, rRNA, and DNA

Answer: (C)

Verified step by step guidance

1. Understand the process of translation initiation: Translation is the process by which ribosomes synthesize proteins using mRNA as a template. The initiation stage involves the assembly of the initiation complex, which is crucial for starting protein synthesis.
2. Identify the key molecules involved: The initiation complex requires mRNA (the template carrying the genetic code), the small ribosomal subunit (which binds to mRNA), the initiator tRNA (carrying the first amino acid, typically methionine), and the large ribosomal subunit (which joins later to complete the ribosome).
3. Eliminate incorrect options: DNA is not involved in translation; it is used during transcription to produce mRNA. RNA polymerase and DNA polymerase are enzymes involved in transcription and DNA replication, respectively, not translation. rRNA is part of the ribosome but does not assemble independently in the initiation complex.
4. Focus on the correct assembly: The small ribosomal subunit binds to the mRNA at the start codon (AUG). The initiator tRNA, carrying methionine, pairs with the start codon. Finally, the large ribosomal subunit joins to complete the initiation complex.
5. Summarize the correct answer: The molecules required to form the initiation complex during translation are mRNA, the small ribosomal subunit, the initiator tRNA, and the large ribosomal subunit.