Question

Contrast the roles of tRNA and mRNA during translation and list all enzymes that participate in the transcription and translation process.

Short answer

Answer: In translation, tRNA brings amino acids to the ribosome and matches them with corresponding codons on the mRNA, while mRNA transmits the genetic information from DNA to direct the sequence of amino acids. Enzymes involved in transcription include RNA polymerase, helicase, and topoisomerase. Enzymes involved in translation consist of aminoacyl-tRNA synthetase, peptidyl transferase, and the release factor.

Step-by-step solution

Identify the roles of tRNA and mRNA in translation

Transfer RNA (tRNA) and messenger RNA (mRNA) are both types of RNA that perform different roles during translation. tRNA: tRNAs are responsible for bringing amino acids to the ribosome, which serves as the site for protein synthesis. Each tRNA has an anticodon that is complementary to a specific codon on the mRNA. tRNA reads the mRNA by binding to a codon using its anticodon, then brings the corresponding amino acid so that it can be added to the growing polypeptide chain. mRNA: mRNA carries the genetic code from DNA in the form of codons. It is transcribed from DNA in the nucleus and then transported to the ribosome for translation. The role of mRNA is to transmit the genetic information encoded in the DNA in order to direct the sequence of amino acids during protein synthesis.

List enzymes involved in transcription

The process of transcription involves the following enzymes: 1. RNA polymerase: This enzyme is responsible for synthesizing RNA from the DNA template by adding complementary RNA nucleotides to form an mRNA molecule. 2. Helicase: This enzyme unwinds the DNA double helix during transcription to access the DNA template. 3. Topoisomerase: This enzyme relieves the tension in the DNA strand that arises due to unwinding by helicase. It temporarily breaks and rejoins the DNA strands allowing them to untwist.

List enzymes involved in translation

The process of translation involves the following enzymes: 1. Aminoacyl-tRNA synthetase: This enzyme catalyzes the esterification of a specific amino acid to its corresponding tRNA to form an aminoacyl-tRNA. This ensures that the correct amino acid is added to the growing polypeptide chain during translation. 2. Peptidyl transferase: This enzyme, which is part of the ribosome, catalyzes the formation of a peptide bond between the amino acid in the A site of the ribosome (that is brought by tRNA) and the growing peptide chain in the P site. 3. Release factor: This protein recognizes the stop codon on the mRNA and promotes the release of the finished polypeptide chain from the ribosome during the termination phase of translation.

Key concepts

Protein Synthesis

Protein synthesis is a critical process in which cells build proteins based on instructions from genes. This process occurs in two main stages: transcription and translation.

In transcription, the genetic code from DNA is transcribed into a complementary strand of mRNA in the nucleus. This mRNA strand then exits the nucleus and travels to the ribosome, a cellular machine that facilitates translation, the second stage of protein synthesis. During translation, the sequence of codons on the mRNA is read, and corresponding amino acids are brought to the ribosome by tRNA. The amino acids are then linked together by peptide bonds to form a polypeptide, or protein chain, in a sequence dictated by the original DNA code.

Enzymes in Transcription and Translation

During the intricate processes of transcription and translation, several important enzymes play vital roles in ensuring accurate and efficient synthesis of proteins.

• RNA Polymerase - In transcription, RNA polymerase binds to a specific section of the DNA and unwinds the DNA strands. It reads the DNA sequence and synthesizes a complementary strand of mRNA.
• Helicase - Helicase assists by unwinding the DNA helix, allowing RNA polymerase to access the genes encoded in DNA.
• Topoisomerase - Works to prevent the DNA from becoming too tangled by making temporary cuts to alleviate the strain caused by unwinding.

In translation, once the mRNA reaches the ribosome, additional enzymes come into play:

• Aminoacyl-tRNA Synthetase - Charges tRNAs with the correct amino acids.
• Peptidyl Transferase - Forms peptide bonds between adjacent amino acids, extending the growing protein chain.
• Release Factor - Recognizes the stop codon which triggers the release of the newly synthesized protein from the ribosome.

Genetic Code Transcription

The process by which the genetic code is transcribed involves copying a segment of DNA into mRNA. The genetic code consists of codons, which are sequences of three nucleotides each. Each codon corresponds to a specific amino acid or a stop signal during protein synthesis.

DNA's double helix is unwound, and RNA polymerase reads one strand of exposed DNA, called the template strand. It pairs complementary RNA nucleotides with the DNA nucleotides, thus creating an mRNA strand. This newly synthesized mRNA strand detaches from the DNA once the end of the gene is reached, and it is then modified and exported from the nucleus to the ribosome for translation. The precise transcription of the genetic code is critical for the accurate translation of the code into functional proteins.

Aminoacyl-tRNA Synthetase Function

The function of aminoacyl-tRNA synthetase is central to the translation process. This enzyme has the crucial role of binding the appropriate amino acid to its corresponding tRNA. This is known as 'charging' the tRNA. Each type of aminoacyl-tRNA synthetase is specific for one amino acid and the set of tRNAs that recognize the codons for that amino acid.

During this process, the enzyme first binds and activates the amino acid with ATP, forming an aminoacyl-adenylate intermediate. The correct tRNA then binds to the enzyme, which transfers the amino acid onto the tRNA, resulting in a charged aminoacyl-tRNA that's ready to deliver its amino acid to the ribosome during protein synthesis. The precision of this charging step is essential, as it establishes the correct translation of the mRNA codons into the sequence of amino acids in the protein.