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Questions and Answers
What is the function of the TATA box in transcription initiation?
Which of the following correctly describes the non-coding strand of DNA?
What role does RNA Polymerase II play during transcription initiation?
Which factor marks the beginning of transcription?
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During elongation in transcription, what does RNA Polymerase do?
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Which element is found about 25 nucleotides upstream of a gene and binds to critical factors?
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What happens once the transcription initiation complex is assembled?
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What is an essential role of Transcription Factors in gene expression?
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What invests GTP to ensure accuracy and efficiency during translation elongation?
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During peptide bond formation, which ribosomal subunit catalyzes the formation of the bond?
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What happens to the tRNA in the P site during the translocation process in translation?
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Which component recognizes a stop codon during translation termination?
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What is hydrolyzed during the final steps of translation?
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In translation, which step involves moving the tRNA from the A site to the P site?
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What gives the analogy of aligning puzzle pieces for the correct mRNA-tRNA binding?
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Which analogy is used to describe the recognition of a stop codon during translation termination?
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What is the function of the modified guanine nucleotide added during capping?
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What is the main role of the poly-A tail in mRNA processing?
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Which process involves the removal of introns from pre-mRNA?
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What is the purpose of adding a poly-A tail to the 3’ end of pre-mRNA?
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Which component is responsible for facilitating the export of mRNA from the nucleus to the cytoplasm?
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What is the main function of splicing in mRNA processing?
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In mRNA processing, what does 5’ capping protect the nascent mRNA from?
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Where do proteins destined for the cytosol complete translation?
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What differentiates proteins destined for the endomembrane system from those destined for the cytosol during translation?
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What is the role of signal recognition particle (SRP) in protein synthesis?
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Which step of protein synthesis involves secretory and membrane proteins taking divergent paths?
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What is the function of fixed ribosomes on the rough ER?
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Which organelle solubilizes secretory proteins during protein synthesis?
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What feature distinguishes free ribosomes from fixed ribosomes?
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Why are proteins continuously produced and function in the cytosol described as 'independent artisans'?
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What is the role of RNA in protein synthesis?
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What is the main function of transcription factors in gene expression?
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What marks the start of transcription for a specific gene?
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Which enzyme recognizes and binds to a promoter sequence near the beginning of a gene during transcription initiation?
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What is the function of repressor transcription factors in gene expression?
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Which type of proteins help determine which genes are turned on or off by binding to nearby DNA?
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In protein synthesis, what comes after the process of transcription?
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Study Notes
Transcription Initiation
- The assembly of transcription factors, including the TATA box binding protein (TBP), forms the transcription initiation complex.
- The TATA box, located about 25 nucleotides upstream of the gene, serves as a crucial binding site for these factors.
- TBP is part of a larger protein complex that includes RNA Polymerase II.
- Once assembled, this complex marks the start of transcription.
Initiation of Transcription
- With the transcription initiation complex in place, RNA Polymerase II binds to it.
- Additional transcription factors also join at the promoter region of the gene.
- This binding signifies the beginning of transcription.
- RNA Polymerase II reads the DNA template strand, synthesizing a complementary RNA strand.
Coding and Non-Coding Strands
- The coding strand of DNA has the same sequence as the RNA transcript, except with Thymine (T) instead of Uracil (U).
- The non-coding strand, also known as the template strand, serves as the template for RNA synthesis.
Elongation
- Once initiated, RNA polymerase begins moving downstream along the gene.
- It reads the DNA strand and adds complementary RNA nucleotides to the growing mRNA (messenger RNA) chain.
- During this process, RNA uses Uracil (U) instead of Thymine (T), pairing Adenine (A) with Uracil.
Gene Expression
- Gene expression is the process of going from DNA to a functional product (protein).
- DNA → RNA → Protein is the sequence of gene expression.
- Genotype refers to an organism's hereditary information, while phenotype refers to the actual observable or physiological traits.
- Genotype and its interactions with the environment determine the phenotype.
Transcription Factors
- Transcription factors are proteins that play a pivotal role in regulating gene expression.
- They help determine which genes are turned on or off by binding to nearby DNA.
- Activator transcription factors enhance gene transcription, while repressor factors decrease it.
Processing of Pre-mRNA to Mature mRNA
- Capping involves adding a modified guanine nucleotide to the 5' end of the pre-mRNA transcript, which serves several critical functions, including protection, ribosome binding, and export.
- Tailing involves adding a sequence of 50 to 250 adenine nucleotides (poly-A tail) to the 3' end of the pre-mRNA transcript, which protects the mRNA from degradation, assists in transporting the mature mRNA, and is involved in binding proteins that initiate translation.
- Splicing is the process of removing introns (non-coding regions) from the pre-mRNA transcript, ensuring efficient resource utilization and contributing to cellular specialization and adaptation.
Protein Synthesis and Vesicular Transport
- Proteins destined for the cytosol are continuously produced and function in the cytosol, completing translation on free ribosomes.
- Proteins destined for the endomembrane system complete translation at fixed ribosomes on the rough ER (RER).
- The ribosome's location determines its function, with fixed ribosomes on the RER specialized for proteins destined for the endomembrane system.
- Signal peptide and signal recognition particle (SRP) are involved in the targeting of proteins to the endomembrane system.
Translation Elongation
- The ribosome reads the mRNA codon in the A site, and the anticodon of the incoming tRNA base pairs with the mRNA codon.
- GTP is invested to ensure accuracy and efficiency.
- The large ribosomal subunit catalyzes the formation of a peptide bond, linking the incoming amino acid to the growing polypeptide chain.
Translation Termination
- When a stop codon (UAA, UAG, or UGA) enters the A site, it's recognized by a release factor.
- The release factor fits neatly into the P site, and the bond between the P-site tRNA and the last amino acid is hydrolyzed.
- This marks the end of translation.
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Description
Test your knowledge on the process of translation elongation, focusing on codon recognition and tRNA binding. Learn how the ribosome acts as a precision instrument and how GTP is used for accuracy and efficiency. Explore the analogy of aligning puzzle pieces for a better understanding of peptide bond formation.