RNA Transcription & Translation
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Questions and Answers

What is the primary role of RNA Polymerase in gene transcription?

  • It translates mRNA into proteins.
  • It catalyzes the formation of phosphodiester bonds between nucleotides. (correct)
  • It facilitates the folding of proteins in the cytoplasm.
  • It binds the mRNA to ribosomes for translation.

Which RNA Polymerase is responsible for transcribing mRNA in eukaryotes?

  • RNA Pol II (correct)
  • RNA Pol I
  • RNA Pol III
  • A single RNA Polymerase

Which structure releases mRNA into the cytoplasm after transcription?

  • Nuclear envelope
  • Endoplasmic reticulum
  • Nuclear pores (correct)
  • Ribosome

How does RNA Polymerase II initiate transcription?

<p>It can start creating an RNA chain without a primer. (B)</p> Signup and view all the answers

What is the main function of ribosomes during translation?

<p>To translate mRNA into a polypeptide chain. (D)</p> Signup and view all the answers

Which RNA Polymerase is NOT found in eukaryotic cells?

<p>Single RNA Polymerase (D)</p> Signup and view all the answers

What process occurs after mRNA is translated by ribosomes?

<p>Folding of polypeptides into active proteins. (C)</p> Signup and view all the answers

What regulates the activity of RNA Polymerase II?

<p>Phosphorylation of its subunits. (C)</p> Signup and view all the answers

What is the primary function of ribosomes during protein translation?

<p>Translating mRNA into proteins (A)</p> Signup and view all the answers

How do tRNAs ensure accurate translation of mRNA?

<p>By wobble base-pairing at the third position (A)</p> Signup and view all the answers

What is the significance of the large subunit of the ribosome?

<p>It catalyzes peptide bonds between amino acids (A)</p> Signup and view all the answers

What are ribosomes primarily composed of?

<p>Two-thirds RNA and one-third proteins (B)</p> Signup and view all the answers

Which statement about the sedimentation coefficients of ribosome subunits is accurate?

<p>The large subunit has a higher sedimentation coefficient than the small subunit (C)</p> Signup and view all the answers

What role does RNA play in ribosome function?

<p>It is responsible for catalytic activity and translation regulation (A)</p> Signup and view all the answers

Which of the following best describes the interaction between ribosomes and mRNA during translation?

<p>Ribosomes bind mRNA and position tRNA for accurate pairing (C)</p> Signup and view all the answers

What results from the activity of peptidyl transferase in the ribosome?

<p>Covalent bonds between amino acids (C)</p> Signup and view all the answers

What is the main function of transfer RNAs (tRNAs)?

<p>To act as adaptors translating the mRNA code to amino acids. (A)</p> Signup and view all the answers

Where does the amino acid attach to the tRNA molecule?

<p>At the amino acid-accepting arm. (C)</p> Signup and view all the answers

What role do aminoacyl-tRNA synthetases play in the process of translation?

<p>They recognize amino acids and attach them to the appropriate tRNA. (A)</p> Signup and view all the answers

What type of bond is formed between the amino acid and the tRNA by the action of aminoacyl-tRNA synthetase?

<p>Covalent bond. (C)</p> Signup and view all the answers

How does the hydrolysis of ATP relate to the action of aminoacyl-tRNA synthetase?

<p>It supplies energy to link the amino acid with tRNA. (A)</p> Signup and view all the answers

What does redundancy in the genetic code refer to?

<p>The fact that some amino acids are encoded by more than one codon. (A)</p> Signup and view all the answers

What does the term 'wobble base-pairing' refer to in the context of tRNA?

<p>The ability of the third nucleotide of the anticodon to bind to multiple codons. (A)</p> Signup and view all the answers

Which component of the tRNA is responsible for matching with the codon on mRNA?

<p>Anticodon loop. (C)</p> Signup and view all the answers

What number of aminoacyl-tRNA synthetases are present in the cell?

<p>20 synthetases, one for each amino acid. (C)</p> Signup and view all the answers

What role do transcription factors (TF) play in transcription initiation?

<p>They help RNA Pol II locate and bind to the core promoter. (C)</p> Signup and view all the answers

During transcription elongation, what role does RNA Pol II perform?

<p>It unwinds the DNA into a transcription bubble. (B)</p> Signup and view all the answers

What signifies the termination of transcription?

<p>The release of RNA Pol II and mRNA at the AAUAAA signal. (C)</p> Signup and view all the answers

How is genetic information translated from RNA to protein?

<p>Through the interpretation of mRNA codons by transfer RNAs (tRNAs). (B)</p> Signup and view all the answers

What is the significance of codons during protein translation?

<p>Each codon specifies one amino acid. (B)</p> Signup and view all the answers

What is true about the redundancy of the genetic code?

<p>Some amino acids can be specified by more than one codon. (B)</p> Signup and view all the answers

What shape do transfer RNAs (tRNAs) take on during their functional structure?

<p>A cloverleaf shape that folds into a complex 3D structure. (B)</p> Signup and view all the answers

Which of the following best describes the process of transcription?

<p>The synthesis of complementary RNA from a DNA template. (D)</p> Signup and view all the answers

What determines which DNA strand serves as the template during transcription?

<p>The orientation of the RNA Pol II enzyme. (A)</p> Signup and view all the answers

What are stop codons and their function in translation?

<p>They mark the end of the polypeptide chain during translation. (D)</p> Signup and view all the answers

What initiates protein synthesis in the ribosome?

<p>The presence of the start codon (AUG) (C)</p> Signup and view all the answers

What is the main role of the ribosome during translation?

<p>To catalyze peptide bond formation (A)</p> Signup and view all the answers

What happens during the elongation phase of translation?

<p>The new tRNA enters the A site of the ribosome (D)</p> Signup and view all the answers

Which site on the ribosome is occupied by the tRNA carrying the growing polypeptide chain?

<p>Peptidyl-tRNA (P) site (B)</p> Signup and view all the answers

What is the function of release factors during termination of translation?

<p>They release the newly formed polypeptide (A)</p> Signup and view all the answers

How does the ribosome move along the mRNA during translation?

<p>In a 5’ to 3’ direction (A)</p> Signup and view all the answers

Which tRNA is always associated with methionine?

<p>Initiator tRNA (A)</p> Signup and view all the answers

What is the primary role of ribozymes?

<p>Act as catalysts for biochemical reactions (A)</p> Signup and view all the answers

What is the outcome when a stop codon is recognized in the A site during translation?

<p>Protein synthesis is terminated (C)</p> Signup and view all the answers

What happens to the tRNA once it has donated its amino acid during elongation?

<p>It enters the E site to be released (C)</p> Signup and view all the answers

What triggers the change in peptidyl transferase activity during termination?

<p>The presence of release factors (D)</p> Signup and view all the answers

What is the final result when the translation termination process is complete?

<p>The amino acid sequence is folded into a functional protein (B)</p> Signup and view all the answers

During the elongation phase, how does the ribosome ensure the correct amino acid is added?

<p>By matching tRNA anticodons with mRNA codons (D)</p> Signup and view all the answers

What is the role of peptide bonds during protein synthesis?

<p>To link amino acids together (D)</p> Signup and view all the answers

Flashcards

Gene Transcription

The process of copying the genetic information from a DNA strand into an RNA molecule.

RNA Polymerase

A large multi-subunit enzyme responsible for catalyzing the synthesis of RNA from a DNA template.

RNA Polymerase II

RNA Polymerase that is responsible for transcribing messenger RNA (mRNA) and other non-coding RNAs.

Transcription Factor

A protein that binds to DNA and helps RNA polymerase to initiate transcription.

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Translation

The process of using the information in an mRNA molecule to synthesize a protein.

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Ribosome

A complex molecular machine composed of ribosomal RNA (rRNA) and proteins, responsible for protein synthesis.

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Transfer RNA (tRNA)

A small RNA molecule that carries a specific amino acid to the ribosome, where it is used to build a protein chain.

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Codon

A sequence of three nucleotides in an mRNA molecule that codes for a specific amino acid.

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Wobble Base Pairing

A phenomenon where some amino acids can be specified by more than one mRNA codon.

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Wobble tRNAs

Those tRNA molecules that can pair with more than one codon due to flexibility at the third position. They have a less stringent requirement for base pairing at the third position of the codon.

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Peptidyl (P) Site

The site in the ribosome where the tRNA carrying the growing polypeptide chain is bound.

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Aminoacyl (A) Site

The site in the ribosome where the incoming tRNA carrying the next amino acid to be added to the polypeptide chain binds.

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Exit (E) Site

The site in the ribosome where the tRNA that has donated its amino acid to the growing polypeptide chain exits.

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Protein Synthesis

The process of translating the genetic code of mRNA into a protein.

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Peptidyl Transferase Activity

The formation of a peptide bond between two amino acids, catalyzed by the ribosome.

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Core Promoter

Non-coding DNA sequence immediately before the target gene, where RNA polymerase II binds to initiate transcription.

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Transcription Factors (TFs)

Proteins that guide RNA polymerase II to the core promoter, enabling the transcription process to start.

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Pre-Initiation Complex

The complex formed by RNA polymerase II and transcription factors, marking the beginning of transcription.

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Transcription Bubble

The process of unwinding the DNA double helix into two separate strands to allow RNA polymerase II to access the template.

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Transcription Elongation

The process where RNA polymerase II moves along the DNA template strand, reading the sequence and adding complementary nucleotides to the growing RNA molecule.

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Termination Signal

A specific nucleotide sequence in the newly formed mRNA that signals the end of transcription.

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Protein Translation

The process of converting genetic information from RNA language into protein language, using different symbols (codons) to represent amino acids.

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tRNA Structure

tRNA molecules are folded into a specific 3D shape, with double-stranded regions and loops. This structure is crucial for their role as adaptors in translation.

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Anticodon Loop

A region of the tRNA molecule containing three consecutive nucleotides that bind to a complementary codon on the mRNA.

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Amino Acid-Accepting Arm

The 3' end of the tRNA molecule where the amino acid is attached.

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Aminoacyl-tRNA Synthetases

Enzymes that catalyze the formation of a covalent bond between a specific amino acid and its corresponding tRNA.

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Amino Acid Charging

The process of linking an amino acid to its corresponding tRNA using energy from ATP hydrolysis.

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Codon Redundancy

A phenomenon where multiple codons can code for the same amino acid, contributing to the genetic code's redundancy.

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Aminoacyl-tRNA Bond

A high-energy bond formed between an amino acid and its corresponding tRNA, providing the energy needed for peptide bond formation during translation.

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Genetic Code

The set of rules that determine the correspondence between mRNA codons and their corresponding amino acids.

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mRNA-binding site

The site within the ribosome where the mRNA molecule binds.

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Aminoacyl-tRNA (A) site

The site within the ribosome where a tRNA carrying an amino acid enters by pairing with the corresponding codon on the mRNA.

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Peptidyl-tRNA (P) site

The site within the ribosome where a tRNA carrying the growing polypeptide chain occupies.

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Translation initiation

The process of assembling a ribosome on an mRNA molecule and initiating protein synthesis.

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Translation elongation

The process of adding amino acids to the growing polypeptide chain during protein synthesis.

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Translation termination

The process of terminating protein synthesis when a stop codon is encountered on the mRNA.

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Initiator tRNA

A special tRNA that carries the amino acid methionine and recognizes the start codon (AUG) on the mRNA during translation initiation.

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Translation initiation factors

A complex of proteins that help facilitate the binding of the initiator tRNA and the small ribosomal subunit to the mRNA during translation initiation.

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Peptidyl transferase

The enzyme responsible for catalyzing the formation of peptide bonds between amino acids during translation.

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Ribosome translocation

The process of moving the ribosome along the mRNA molecule in the 5' to 3' direction, codon by codon, during translation elongation.

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Anticodon

A sequence of three nucleotides on tRNA that base pairs with a complementary codon on mRNA during translation.

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Stop codons

Three specific codons (UAA, UAG, UGA) on mRNA that signal the termination of translation.

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Study Notes

RNA Transcription & Translation

  • RNA transcription is the process where DNA information is copied into RNA.
  • This process is catalyzed by RNA Polymerase enzymes.
  • RNA Polymerase II is a large multiprotein complex, consisting of 12 subunits(RBP1-12). RPB1 the DNA-directed RNA polymerase II subunit catalyzes the transcription of DNA to mRNA.
  • Phosphorylation of RPB1 regulates enzyme activity.
  • RNA Polymerase II cannot "read" DNA; it needs transcription factors for DNA binding and transcription.
  • RNA Polymerase II can start creating an RNA chain without a primer.
  • In eukaryotes, there are three RNA Polymerases:
    • RNA Pol I transcribes ribosomal RNA (rRNA).
    • RNA Pol II transcribes mRNA and most non-coding RNAs.
    • RNA Pol III transcribes tRNA and other.
  • Prokaryotes use only one RNA Polymerase.
  • The process of transcription has three steps:
    • Initiation: RNA Pol II binds to a non-coding DNA sequence before the gene (core promoter). It's guided to this region by transcription factors (TF). RNA Pol II and transcription factors form the pre-initiation complex. RNA Pol II phosphorylation at RBP1 initiates transcription.
    • Elongation: RNA Pol II is released from the promoter and unwinds the DNA into two separate strands ("transcription bubble"). RNA Pol II moves along one strand, using it as a template to synthesize a complementary RNA sequence. Either strand can be a template. RNA Pol II adds nucleotides to the 3' end of the growing RNA molecule.
    • Termination: RNA Pol II encounters a termination signal (AAUAAA hexamer in newly formed mRNA) and transcription stops. RNA Pol and mRNA are released, and the DNA double helix reforms. A new cycle of transcription begins.

Protein Translation - Reading the code

  • Translation converts genetic information from RNA language into protein language.
  • Translation involves reading mRNA in groups of three nucleotides (codons), each specifying an amino acid.
  • There are 4 different nucleotides in mRNA (A, U, G, C).
  • There are 20 different amino acids in proteins.
  • Codons can specify more than one amino acid — the code is redundant.
  • AUG is the start codon (methionine).
  • There are three stop codons (UAA, UAG, UGA).

Transfer RNAs (tRNAs)

  • tRNAs are small RNA molecules folded into a cloverleaf shape (2D shape), with 80 nucleotides.
  • tRNA folds into a complex 3D structure with base pairs forming between different molecule parts.
  • tRNAs act as adaptors translating the mRNA code to the corresponding amino acid.
  • Anticodon loop contains the anticodon (three consecutive nucleotides). Anticodon pairs with the complementary codon on mRNA.
  • The amino acid attaches to the short single-stranded region at the 3' end (amino acid-accepting arm).

Ribosomes translate mRNA into protein

  • mRNA is released from the nucleus into the cytoplasm and attached to ribosomes.
  • Ribosomes translate mRNA into polypeptide chains.
  • Free ribosomes translate proteins that remain in the cytoplasm, while others are incorporated into mitochondria or the nucleus or endoplasmic reticulum ribosomes.
  • Endoplasmic reticulum ribosomes translate proteins that are incorporated into the cell membrane or are destined to be released by the cell.

Ribosomes

  • Protein translation is done by ribosomes.
  • Ribosomes bind to mRNA and position correct tRNA molecules.
  • Ribosomes catalyze peptide bond formation between amino acids.
  • Ribosomes are large complexes made of proteins (ribosomal proteins) and RNA (ribosomal RNAs).
  • They are composed of a large subunit and a small subunit.
  • Small subunit matches tRNA to the mRNA codon.
  • Large subunit catalyzes peptide bonds between amino acids.
  • Ribosomes have sedimentation coefficients (S units).

Ribosome structure

  • Ribosomes are 2/3 RNA and 1/3 protein by weight.
  • RNA is responsible for catalytic activity and regulation of translation.
  • RNA folds into 3D structures forming binding sites for tRNAs and catalytic sites for peptidyl transferase.
  • Some RNA molecules can act as enzymes (ribozymes).
  • Proteins are involved in folding and stabilizing the RNA structure.

Ribosome function

  • The small and large ribosomal subunits assemble near the 5' end of an mRNA.
  • The ribosome moves in a 5' to 3' direction, translating nucleotide sequences into amino acid sequences. It uses tRNAs as adaptors.
  • Each amino acid is added to the end of the polypeptide chain.
  • When protein synthesis is complete, the subunits separate.

Mechanism of protein translation

  • Initiation: The tRNA recognizing the start codon (initiator tRNA) binds to the small ribosomal subunit and scans the mRNA until it finds the start codon (AUG). The large subunit joins.
  • Elongation: The ribosome moves in a 5' to 3' direction, translating codons into amino acids. The correct tRNA is added to the A site. Peptidyl transferase activity forms the peptide bond. The tRNA moves to the E site then the P site, allowing a new tRNA to attach to the A-site.
  • Termination: The presence of a stop codon (UAA, UAG, or UGA in the A site) signals the end of translation. Release factors bind to the stop codon. The polypeptide is released, and the ribosomal subunits dissociate.
  • Ribosome binding sites:
    • mRNA-binding (mRNA is bound to the ribosome).
    • Aminoacyl-tRNA (A)-site: tRNA with amino acid enters.
    • Peptidyl-tRNA (P)-site: tRNA holding growing polypeptide chain sits.
    • Exit (E)-site: Used tRNA exits.

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Description

This quiz covers the essential processes of RNA transcription and translation, focusing on the role of RNA Polymerase and the various steps involved. You'll explore the differences between eukaryotic and prokaryotic transcription mechanisms and the importance of transcription factors. Test your understanding of how RNA is synthesized from DNA!

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