To evaluate the accuracy and sequencing of the descriptions provided, let's break down the process of translation and identify which statements correctly describe it.
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A tRNA molecule containing an amino acid enters the ribosome at the P site.
- Incorrect. tRNA molecules enter at the A site (aminoacyl site) first, not the P site (peptidyl site).
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The elongating polypeptide/protein is synthesized at the P site of the ribosome.
- Correct. The elongating polypeptide chain is indeed formed at the P site, where the tRNA carrying the growing polypeptide is located.
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The mRNA is read three bases at a time which corresponds to a particular amino acid.
- Correct. This statement accurately describes the process called codon recognition, where each codon (three bases) on mRNA corresponds to a specific amino acid.
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A tRNA molecule containing an amino acid enters the ribosome at the A site before moving to the P site.
- Correct. This accurately describes the process where a new tRNA carrying an amino acid enters at the A site before translocating to the P site after peptide bond formation.
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tRNA molecules are reconnected with an amino acid before exiting the ribosome so the process can continue.
- Incorrect/partially correct. While tRNAs are indeed recharged with amino acids by aminoacyl-tRNA synthetases before entering the ribosome, they do not necessarily exit the ribosome in that state. The tRNAs exit after delivering their amino acid, but "reconnected" implies a different context that isn’t typically stated in this manner.
Summary
The accurate statements regarding translation are:
- B (The elongating polypeptide/protein is synthesized at the P site of the ribosome.)
- C (The mRNA is read three bases at a time which corresponds to a particular amino acid.)
- D (A tRNA molecule containing an amino acid enters the ribosome at the A site before moving to the P site.)
So, the correct choices are B, C, and D.