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Questions and Answers
What does degeneracy in the genetic code refer to?
What does degeneracy in the genetic code refer to?
Which of the following correctly describes stop codons?
Which of the following correctly describes stop codons?
What is the role of the AUG codon in translation?
What is the role of the AUG codon in translation?
How many different combinations of codons can be formed with three nucleotides?
How many different combinations of codons can be formed with three nucleotides?
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What happens during translation when an open reading frame (ORF) is identified?
What happens during translation when an open reading frame (ORF) is identified?
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What distinguishes the reading frames during translation?
What distinguishes the reading frames during translation?
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Which characteristic of the genetic code indicates it is quasi-universal?
Which characteristic of the genetic code indicates it is quasi-universal?
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Which of the following is NOT a feature of the genetic code?
Which of the following is NOT a feature of the genetic code?
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What is the primary function of tRNA in translation?
What is the primary function of tRNA in translation?
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What makes up the prokaryotic ribosome?
What makes up the prokaryotic ribosome?
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Which component is essential for the elongation phase of translation?
Which component is essential for the elongation phase of translation?
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Which of the following correctly describes the ribosome during protein synthesis?
Which of the following correctly describes the ribosome during protein synthesis?
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What is the significance of the anticodon in tRNA?
What is the significance of the anticodon in tRNA?
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How many ribosomes are typically found in an E. coli cell?
How many ribosomes are typically found in an E. coli cell?
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What are release factors responsible for during translation?
What are release factors responsible for during translation?
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Which of the following correctly describes the ribosomal RNA components in eukaryotic ribosomes?
Which of the following correctly describes the ribosomal RNA components in eukaryotic ribosomes?
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What is the role of the 5’ base of the anticodon in tRNA?
What is the role of the 5’ base of the anticodon in tRNA?
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What is the function of aminoacyl tRNA synthetases?
What is the function of aminoacyl tRNA synthetases?
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Which factor is NOT involved in the initiation complex of prokaryotic translation?
Which factor is NOT involved in the initiation complex of prokaryotic translation?
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What is the role of the Shine-Dalgarno sequence in prokaryotic translation?
What is the role of the Shine-Dalgarno sequence in prokaryotic translation?
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What is produced when adenosine monophosphate (AMP) is added to an amino acid during tRNA charging?
What is produced when adenosine monophosphate (AMP) is added to an amino acid during tRNA charging?
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Which of the following bases might be found in the anticodon of a tRNA?
Which of the following bases might be found in the anticodon of a tRNA?
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What is the first step in the initiation of prokaryotic translation?
What is the first step in the initiation of prokaryotic translation?
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How many initiation factors are involved in the assembly of the prokaryotic ribosome during translation initiation?
How many initiation factors are involved in the assembly of the prokaryotic ribosome during translation initiation?
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What occurs simultaneously in prokaryotes allowing for rapid cellular response?
What occurs simultaneously in prokaryotes allowing for rapid cellular response?
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Where does transcription occur in eukaryotic cells?
Where does transcription occur in eukaryotic cells?
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What type of modifications may occur after a protein is synthesized?
What type of modifications may occur after a protein is synthesized?
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Why are bacterial ribosomes targeted by antibacterial drugs?
Why are bacterial ribosomes targeted by antibacterial drugs?
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What crucial step is necessary in eukaryotic cells before translation can occur?
What crucial step is necessary in eukaryotic cells before translation can occur?
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What role do post-translational modifications serve for proteins?
What role do post-translational modifications serve for proteins?
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Which ribosome subunits do major classes of protein synthesis inhibitors target?
Which ribosome subunits do major classes of protein synthesis inhibitors target?
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What is a consequence of the separation of transcription and translation in eukaryotes?
What is a consequence of the separation of transcription and translation in eukaryotes?
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What is the role of the ribosome binding site (RBS) in prokaryotes?
What is the role of the ribosome binding site (RBS) in prokaryotes?
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What is unique about the initiator tRNA that interacts with the AUG codon in prokaryotes?
What is unique about the initiator tRNA that interacts with the AUG codon in prokaryotes?
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In eukaryotes, what does the initiation complex recognize to begin translation?
In eukaryotes, what does the initiation complex recognize to begin translation?
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What is the primary function of the E (exit) site in the ribosome?
What is the primary function of the E (exit) site in the ribosome?
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Why are methionine (Met) residues not always the first amino acids in mature proteins?
Why are methionine (Met) residues not always the first amino acids in mature proteins?
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What happens to the ribosome after it recognizes the start codon in eukaryotic translation?
What happens to the ribosome after it recognizes the start codon in eukaryotic translation?
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How does the eukaryotic ribosome locate the correct start codon?
How does the eukaryotic ribosome locate the correct start codon?
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Which site on the ribosome is primarily responsible for peptide bond formation?
Which site on the ribosome is primarily responsible for peptide bond formation?
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What triggers the termination of protein synthesis during translation?
What triggers the termination of protein synthesis during translation?
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Which codons are considered stop codons in the context of translation termination?
Which codons are considered stop codons in the context of translation termination?
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What is formed when multiple ribosomes translate a single mRNA simultaneously?
What is formed when multiple ribosomes translate a single mRNA simultaneously?
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In prokaryotes, what allows transcription and translation to occur simultaneously?
In prokaryotes, what allows transcription and translation to occur simultaneously?
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What happens to the ribosomal subunits after the newly made protein is released?
What happens to the ribosomal subunits after the newly made protein is released?
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What is the role of release factors (RFs) during translation termination?
What is the role of release factors (RFs) during translation termination?
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What is the direction of mRNA reading during translation?
What is the direction of mRNA reading during translation?
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During bacterial translation initiation, which component is included in the initiation complex?
During bacterial translation initiation, which component is included in the initiation complex?
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Study Notes
Translation of mRNA into Proteins
- Translation converts mRNA sequences into polypeptide chains.
- It's the final step in using genetic information encoded in DNA.
Transcription
- DNA instructions are transcribed onto mRNA.
- Ribosomes read mRNA to assemble amino acids into proteins.
RNA Processing
- Primary RNA transcript undergoes processing.
- Exons are joined together and introns are removed.
- Spliced RNA is the final product.
Translation (detailed)
- mRNA is read in three-nucleotide segments (codons).
- Each codon corresponds to a specific amino acid.
- The genetic code defines the correspondence between codons and amino acids.
- Codons start from the 5' end of the mRNA.
- Sixty-one codons code for twenty amino acids.
- Three codons (UAG, UGA, UAA) are stop codons, signaling the end of translation.
- AUG is a start codon, typically specifying methionine.
- Translation proceeds in a specific reading frame, typically beginning at AUG.
Features of the Genetic Code
- Quasi-universal: Similar genetic code is used by most species.
- Degenerate: Multiple codons code for some amino acids. Reduces harmful impact of mutations.
- Comma-less and non-overlapping: Codons are read as distinct segments, not overlapping.
Ribosomes
- Ribosomes are complex macromolecular organelles.
- Made of RNA and proteins (ribozymes and structural RNAs).
- Bacterial ribosomes are 70S (50S and 30S subunits).
- Eukaryotic ribosomes are 80S (60S and 40S subunits).
- Ribosomes are abundant sites of protein synthesis.
- They dissociate and reassociate during translation.
Transfer RNAs (tRNAs)
- Key link between mRNA and protein synthesis.
- tRNAs are specific for each amino acid. They have an anticodon that pairs with mRNA codons.
- tRNAs carry the specific amino acid to the ribosome.
- tRNAs have a three-dimensional structure.
- One end holds an amino acid; the other anticodon.
- A single tRNA can base pair with more than one codon.
Initiation of Translation (prokaryotes)
- Ribosomes assemble around mRNA.
- Initiator tRNA (carrying methionine) binds to the start codon (AUG).
- Specific initiation factors involved.
Elongation of the Polypeptide Chain
- Ribosome moves along mRNA in the 5' to 3' direction
- tRNA carrying the next amino acid enters the A-site
- Peptide bonds form between amino acids.
- Ribosome translocates along the mRNA.
- tRNA moves to the E-site.
- The process repeats until a stop codon is reached.
Termination of Translation
- Stop codons (UAA, UAG, UGA) signal termination.
- Release factors bind to the stop codon.
- Polypeptide chain is released.
- Ribosome subunits dissociate.
Post-translational Modifications
- Proteins undergo modifications after synthesis.
- These modifications can include removal of parts, addition of fats, sugars, or small chemical groups.
- The modifications are often critical for protein function.
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Description
Test your knowledge on the intricacies of the genetic code and the process of translation. This quiz covers topics such as codons, tRNA functions, ribosome composition, and the nuances of stop codons. Perfect for students studying genetics or molecular biology.
