Problem 4 - AP Biology Premium Prep 2021

Question

If a messenger RNA codon is UAC, which of the following would be the complementary anticodon triplet in the transfer RNA? (A) ATG (B) \(\mathrm{AUC}\) (C) \(\mathrm{AUG}\) (D) ATT

Step-by-Step Solution

Answer

The complementary anticodon triplet for the given mRNA codon UAC is \(\mathrm{AUG}\), which corresponds to the correct answer (C).

Step 1: Written codon

We are given the mRNA codon UAC.

Step 2: Base pairing rules

Remember the base pairing rules for mRNA to tRNA: - A pairs with U - C pairs with G - G pairs with C - U pairs with A

Step 3: Find the complementary anticodon triplet

Using the base pairing rules, the anticodon triplet that complements the given mRNA codon (UAC) can be found as follows: - U pairs with A - A pairs with U - C pairs with G So, the complementary anticodon triplet is AUG.

Step 4: Choose the correct answer

Now that we found the anticodon triplet (AUG), let's identify the correct answer from the given options: (A) ATG (B) \(\mathrm{AUC}\) (C) \(\mathrm{AUG}\) (D) ATT The correct answer is (C) \(\mathrm{AUG}\).

Key Concepts

Base Pairing Rules

Understanding base pairing rules is essential in the field of genetics because they are the foundation of genetic coding. These rules dictate how bases on the DNA and RNA strands interact with each other. When it comes to RNA and its interaction with transfer RNA (tRNA), the rules are quite straightforward:

• Adenine (A) pairs with Uracil (U).
• Cytosine (C) pairs with Guanine (G).
• Guanine (G) pairs with Cytosine (C).
• Uracil (U) pairs with Adenine (A).

These base pairing rules ensure that the genetic code is accurately transcribed and translated into proteins. Unlike DNA, where Thymine (T) pairs with Adenine (A), in RNA, Uracil (U) substitutes for Thymine.
This difference is critical in processes like transcription and translation, where mRNA and tRNA work together to produce proteins.

mRNA

Messenger RNA or mRNA plays a crucial role in the process of translating genetic information from DNA to proteins. It serves as the intermediary that carries genetic instructions from the DNA in the cell nucleus to the ribosomes, where protein synthesis occurs.
In the transcription process, an mRNA strand is formed by using DNA as a template. This mRNA strand is composed of codons, which are sequences of three nucleotides that correspond to specific amino acids or stop signals during protein synthesis. For instance, in our example, the codon given is UAC.
The accuracy of mRNA transcription and translation is significant because any errors in this process can lead to incorrect amino acids being added in the protein chain, potentially causing malfunctioning proteins.

tRNA

Transfer RNA, abbreviated as tRNA, is essential in translating the genetic code contained in mRNA into protein structures. tRNAs are key actors in the translation phase of protein synthesis, wherein each tRNA molecule carries a specific amino acid to the ribosome.
tRNA molecules have a unique cloverleaf structure and contain an anticodon region, which is crucial for recognizing and binding to specific codons on the mRNA strand. For instance, for the mRNA codon UAC, the tRNA anticodon would be AUG, following the base pairing rules.
tRNAs ensure that the correct amino acids are added to the growing protein chain, helping build the protein's primary structure efficiently and accurately.

Anticodon Triplet

An anticodon triplet is a crucial component of tRNA molecules, consisting of three nucleotides that match the complementary codon on the mRNA strand. This matching process ensures the correct amino acid sequence in the resulting protein.
In the example problem, the mRNA codon UAC requires a complementary tRNA anticodon, which, according to base pairing rules, is AUG. This process of matching codons to anticodons helps to accurately translate the genetic message into a functional protein.
The anticodon-codon interaction is critical for maintaining the accuracy of protein synthesis, as tRNA molecules must bring the correct amino acids to the ribosomes based on the sequence signaled by the mRNA, thus enabling precise assembly of proteins.