Problem 8 - Campbell Biology Concepts & Connections

Question

The nucleotide sequence of a DNA codon is GTA. A messenger RNA molecule with a complementary codon is transcribed from the DNA. In the process of protein synthesis, a transfer RNA pairs with the mRNA codon. What is the nucleotide sequence of the tRNA anticodon? a. CAT b. CUT c. GUA d. CAU

Step-by-Step Solution

Answer

The nucleotide sequence of the tRNA anticodon is GUA.

Step 1: Identify the DNA Codon

The given DNA codon is GTA.

Step 2: Transcribe the mRNA Codon

To find the mRNA codon, replace each DNA base with its complementary base: G to C, T to A, and A to U. Thus, the mRNA codon transcribed from GTA is CAU.

Step 3: Determine the tRNA Anticodon

The tRNA anticodon is complementary to the mRNA codon. Replace each mRNA base with its complementary base: C to G, A to U, and U to A. Therefore, the tRNA anticodon for the mRNA codon CAU is GUA.

Step 4: Select the Correct Answer

The nucleotide sequence of the tRNA anticodon is GUA, which corresponds to option c.

Key Concepts

DNA transcription

DNA transcription is the process where a specific segment of DNA is used as a template to produce messenger RNA (mRNA). This is the first step in gene expression. During transcription, RNA polymerase reads the DNA sequence and forms a complementary mRNA strand. The base pairing rules are simple:

• Adenine (A) pairs with Uracil (U) in RNA, instead of Thymine (T) in DNA.
• Thymine (T) pairs with Adenine (A).
• Cytosine (C) pairs with Guanine (G), and vice versa.

As an example, if the DNA sequence is GTA, the transcribed mRNA sequence would be CAU.

mRNA codon

An mRNA codon is a set of three nucleotides within the mRNA that specifies a particular amino acid or a start/stop signal during protein synthesis. These codons are interpreted by the ribosome where the translation of the mRNA into a protein occurs. Codons are pivotal in translating genetic information from the DNA into the language of proteins. For instance, in the DNA codon 'GTA', the mRNA transcribed is 'CAU'. Each triplet codon, like 'CAU', codes for a specific amino acid when the protein is formed.

protein synthesis

Protein synthesis is the process of creating proteins from the information encoded in mRNA. It involves two main stages:

• Transcription: where DNA is converted to mRNA.
• Translation: where mRNA is used as a template to build amino acid chains (proteins).

The ribosome reads the mRNA codons and uses tRNA molecules to deliver specific amino acids to build a protein. Each tRNA has an anticodon that matches the mRNA codon, ensuring that the correct amino acid is added to the chain. For instance, the mRNA codon 'CAU' has a complementary tRNA anticodon 'GUA'.

complementary base pairing

Complementary base pairing is the specific hydrogen bonding between purines and pyrimidines in DNA and RNA.
In DNA, Adenine (A) pairs with Thymine (T) and Guanine (G) pairs with Cytosine (C). In RNA, Adenine (A) pairs with Uracil (U) instead of Thymine (T). Complementary base pairing ensures accurate transcription of DNA to mRNA and correct pairing between mRNA codons and tRNA anticodons during protein synthesis. For example, if the mRNA codon is 'CAU', the tRNA anticodon will be 'GUA', following the base pairing rules of C to G, A to U, and U to A.