Translation (Protein Synthesis) Questions and Answers (PDF)

Translation is the process of synthesizing proteins from mRNA in cells. It occurs in the cytoplasm, where ribosomes decode mRNA sequences. This process involves three key stages: initiation, elongation, and termination. Ribosomes, tRNAs, and various enzymes play crucial roles in translation. It is essential for gene expression and cellular function. This articles about Translation Questions and Answers. You can download all the questions with answer as PDF from the download link provided below the post.

Molecular Biology Notes | Molecular Biology PPTs | Molecular Biology MCQs

1. What is the role of ribosomes in the translation process?

Ribosomes facilitate the translation of mRNA into a polypeptide chain. They consist of a small and a large subunit, which come together to read the mRNA sequence. The small subunit binds to the mRNA, while the large subunit catalyzes peptide bond formation between amino acids. Ribosomes ensure proper alignment of mRNA and tRNA during elongation. Their structure allows them to move along the mRNA, codon by codon. They terminate the process when a stop codon is encountered. Ribosomes are thus central to protein synthesis in both prokaryotic and eukaryotic cells.

2. What is the significance of tRNA in protein synthesis?     

tRNA (transfer RNA) is essential for translating mRNA codons into amino acids. Each tRNA molecule has an anticodon that pairs with a specific mRNA codon. It carries an amino acid corresponding to that codon, facilitating its addition to the growing polypeptide chain. The structure of tRNA allows it to interact with ribosomes, positioning the amino acid correctly during peptide bond formation. tRNA charging, where it is loaded with the correct amino acid by aminoacyl-tRNA synthetases, is critical for accuracy in translation. tRNAs ensure that the genetic code is interpreted correctly. Their function is pivotal in maintaining the fidelity of protein synthesis.

3. Describe the initiation stage of translation in eukaryotes.

The initiation stage in eukaryotic translation involves the assembly of the translation machinery on the mRNA. The small ribosomal subunit, along with initiation factors and a charged tRNA carrying methionine, binds to the 5′ cap of the mRNA. It scans the mRNA in the 5′ to 3′ direction to locate the start codon, typically AUG. Once the start codon is recognized, the large ribosomal subunit joins to form the complete ribosome. This step positions the methionine-tRNA in the ribosome’s P-site. The assembled ribosome is now ready to begin elongation. Initiation is crucial for ensuring that translation starts at the correct position on the mRNA.

4. What occurs during the elongation phase of translation?

Elongation is the phase where amino acids are sequentially added to the growing polypeptide chain. The ribosome moves along the mRNA, reading each codon and bringing in the corresponding charged tRNA. The aminoacyl-tRNA enters the ribosome’s A-site, and a peptide bond forms between the amino acid at the P-site and the new amino acid. The ribosome then shifts the mRNA-tRNA complex, moving the uncharged tRNA to the E-site and the newly formed peptide chain to the P-site. This process repeats, allowing the chain to lengthen as more amino acids are added. Elongation continues until a stop codon is reached. This stage requires energy in the form of GTP.

5. How does translation terminate when a stop codon is encountered?   

Termination occurs when a ribosome reaches a stop codon on the mRNA, such as UAA, UAG, or UGA. These codons do not correspond to any tRNA, so no aminoacyl-tRNA enters the A-site. Instead, release factors bind to the ribosome at the stop codon position. These factors catalyze the release of the completed polypeptide chain from the tRNA at the P-site. The ribosomal subunits then disassemble and release the mRNA. This process concludes the translation of the mRNA into a protein. Termination is essential for the proper release and folding of newly synthesized proteins.

6. What is the role of aminoacyl-tRNA synthetases in translation?

Aminoacyl-tRNA synthetases are enzymes that attach the correct amino acid to its corresponding tRNA. Each synthetase is specific to a particular amino acid and its compatible tRNAs. This charging process is critical for maintaining the fidelity of the genetic code during translation. The enzyme catalyzes the formation of a covalent bond between the amino acid and the tRNA’s 3’ end. Accurate charging ensures that the tRNA delivers the appropriate amino acid to the ribosome during translation. Errors in this process can lead to the incorporation of incorrect amino acids into the polypeptide chain. Thus, these enzymes play a crucial role in protein synthesis.

7. What is the function of the Shine-Dalgarno sequence in prokaryotic translation?

The Shine-Dalgarno sequence is a ribosomal binding site found in the mRNA of prokaryotes. It is located upstream of the start codon and helps align the ribosome with the start site of translation. The sequence is complementary to a region in the small ribosomal subunit, allowing for proper pairing and positioning. This interaction ensures that the start codon is accurately positioned within the ribosome’s P-site. Proper alignment by the Shine-Dalgarno sequence is essential for accurate initiation of translation. It prevents the ribosome from starting translation at incorrect sites. This sequence is key to efficient protein synthesis in prokaryotes.

8. How do eukaryotic and prokaryotic translation differ in their mechanisms?

Eukaryotic and prokaryotic translation differ in initiation, ribosome structure, and mRNA processing. Eukaryotic initiation relies on the 5′ cap structure and scanning for the start codon, while prokaryotic translation uses the Shine-Dalgarno sequence. Eukaryotic ribosomes are larger (80S) compared to prokaryotic ribosomes (70S). Eukaryotic mRNAs are typically monocistronic and undergo extensive post-transcriptional modifications, such as splicing and polyadenylation. In contrast, prokaryotic mRNAs are often polycistronic and lack such modifications. Translation and transcription are coupled in prokaryotes, while they occur in separate cellular compartments in eukaryotes. These differences reflect adaptations to cellular complexity.

9. What is the role of GTP in the translation process?

GTP serves as an energy source during several steps of translation. It is required for the binding of the aminoacyl-tRNA to the A-site of the ribosome during elongation. GTP is also involved in the translocation of the ribosome along the mRNA, moving tRNAs from one site to the next. Specific translation factors, such as elongation factor G, use GTP hydrolysis for their function. Additionally, initiation and termination stages involve GTP for the assembly and disassembly of the translation machinery. The hydrolysis of GTP ensures that these processes are energetically favorable. It plays a critical role in maintaining the efficiency and directionality of translation.

10. How does the structure of mRNA influence translation efficiency?

The structure of mRNA affects the rate and accuracy of translation. Elements like the 5′ cap, poly(A) tail, and untranslated regions (UTRs) regulate ribosome binding and stability. Secondary structures in the mRNA, such as hairpins, can impede ribosome progression, reducing translation speed. The presence of upstream open reading frames (uORFs) in the 5′ UTR can regulate translation by influencing ribosome scanning. Additionally, codon usage bias, where certain codons are preferred over others, can affect the availability of corresponding tRNAs. A well-structured mRNA ensures efficient and controlled protein synthesis. These factors contribute to the precise regulation of gene expression.

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