Problem 3 - Campbell Biology

Question

The anticodon of a particular tRNA molecule is \begin{equation}\begin{array}{l}{\text { (A) complementary to the corresponding mRNA codon. }} \\ {\text { (B) complementary to the corresponding triplet in rRNA. }} \\ {\text { (C) the part of tRNA that bonds to a specific amino acid. }} \\ {\text { (D) catalytic, making the tRNA a ribozyme. }}\end{array}\end{equation}

Step-by-Step Solution

Answer

The anticodon of a tRNA molecule is complementary to the mRNA codon. (A)

Step 1 - Understanding tRNA and its Function

tRNA (transfer RNA) is a type of RNA that helps decode a messenger RNA (mRNA) sequence into a protein. It does this by carrying an amino acid to the ribosome during translation.

Step 2 - Define Anticodon

An anticodon is a sequence of three nucleotides in a tRNA molecule, corresponding to a complementary codon in mRNA.

Step 3 - Identify the Correct Answer

Given the options, the one that correctly describes the anticodon of a tRNA molecule is that it is complementary to the corresponding mRNA codon.

Step 4 - Eliminate Incorrect Options

Option (B) refers to rRNA, not mRNA. Option (C) describes the amino acid attachment site of tRNA, not the anticodon. Option (D) incorrectly states that the anticodon is catalytic, which is not its function.

Step 5 - Conclusion

The correct statement is that the anticodon is complementary to the corresponding mRNA codon.

Key Concepts

anticodon

Anticodons are vital components of tRNA whose primary role is during protein translation. An anticodon consists of a sequence of three nucleotides on the tRNA molecule. These three nucleotides are complementary to specific mRNA codons.
The anticodon ensures that the tRNA brings the correct amino acid during protein synthesis, aligning with the corresponding codon on the mRNA. This precise matching is crucial for the accurate translation of genetic information from mRNA to proteins.
Considering its function, the anticodon does not bond with rRNA nor is it catalytic. Instead, it specifically pairs with an mRNA codon, ensuring the correct sequence of amino acids in the resulting protein.

mRNA codon

mRNA codons are sequences of three nucleotides on the messenger RNA (mRNA) that encode specific amino acids. During protein translation, the ribosome reads these codons in a sequential manner from the mRNA strand.
Each mRNA codon corresponds to a particular amino acid or a stop signal during protein synthesis. The relationship between mRNA codons and amino acids is defined by the genetic code.
The anticodon of tRNA pairs with the mRNA codon, ensuring the right amino acid is added to the growing polypeptide chain. This complementary pairing is like a lock and key mechanism, maintaining the fidelity of protein synthesis. For example, if an mRNA codon is 'AUG,' the corresponding anticodon on the tRNA would be 'UAC'.

protein translation

Protein translation is the biological process where the ribosome decodes the mRNA sequence into a polypeptide or protein. This happens in several stages: initiation, elongation, and termination.
During initiation, the ribosome assembles around the mRNA and the initial tRNA starts the process. Elongation is the phase where tRNA molecules bring amino acids to the ribosome in the sequence dictated by the mRNA codons. Termination occurs when a stop codon is reached, signaling the ribosome to release the completed polypeptide.
The translation process relies heavily on the accuracy of codon-anticodon pairing. The anticodon on the tRNA must correctly match the mRNA codon to ensure the right amino acid sequence in the protein. Any mistake can result in a malfunctioning protein, which can lead to cellular and organismal issues.

amino acid attachment

Amino acid attachment is a step in the process of preparing tRNA for protein synthesis. Each tRNA molecule carries a specific amino acid, linked to the tRNA by an enzyme called aminoacyl-tRNA synthetase.
This attachment site on the tRNA is distinct from the anticodon. The enzyme ensures the correct amino acid is attached to its corresponding tRNA, based on the anticodon sequence.
The process works as follows:

• The enzyme binds to an amino acid and ATP, becoming activated.
• It then attaches the activated amino acid to the tRNA, forming a high-energy bond.
• Finally, the tRNA with its attached amino acid is ready to deliver it to the growing polypeptide chain at the ribosome during translation.

Proper amino acid attachment is critical for accurate protein synthesis and cellular function.