45 Questions
Which of the following is the final product of gene expression?
C. Polypeptide chain
What is the main function of translation?
D. Synthesis of protein
What is the role of the genetic code?
C. To determine the sequence of amino acids in a protein
Which molecule is responsible for transporting amino acids during translation?
tRNA
What is the role of ribosomes in translation?
To 'decode' the RNA and catalyze the formation of peptide bonds
What is the function of the wobble base in tRNA molecules?
To allow base-pairing with more than one codon
What is the role of aminoacyl-tRNA synthetases in translation?
To attach amino acids to the correct tRNA
True or false: The large and small ribosome subunits are normally separated in the cytoplasm until they are used for translation.
False
Which of the following is true about the initiation of translation?
Met-tRNA binds to both large and small ribosomal subunits to initiate translation
Which of the following is required for the initiation of translation?
mRNA with intact 5'-cap
What is the role of release factor in translation?
It facilitates the termination of translation
Which of the following is true about the initiation step of translation in eukaryotes?
The initiation factors dissociate and assemble with the small ribosomal subunit
Which of the following is true about the elongation step of translation?
The peptide bond between amino acids in the A and P sites is formed by peptidyltransferase
Which of the following is true about the termination step of translation?
Termination occurs when a stop codon is reached
Why are inhibitors of prokaryotic protein synthesis useful as antibiotics?
They inhibit bacterial ribosomes with low toxicity to humans
Which of the following is true about the genetic code?
It is responsible for the synthesis of polypeptide chains.
What is the process by which the genetic code is translated into a polypeptide chain?
Translation
Which of the following is involved in the process of translation?
mRNA
What is the final product of gene expression?
Polypeptide chain
What is the role of aminoacyl-tRNA synthetases in translation?
They catalyze the attachment of amino acids to tRNA molecules.
What is the function of the wobble base in tRNA molecules?
It allows for flexibility in base pairing with mRNA codons.
What is the role of ribosomes in translation?
They facilitate the assembly of amino acids into polypeptide chains.
Which of the following is true about the genetic code?
There are 20 amino acids and 64 possible triplet codes
What is the role of tRNA in translation?
To transport amino acids
What is the function of ribosomes in translation?
To 'read' mRNA and create peptide bonds
What is the role of the wobble base in tRNA molecules?
To allow tRNA molecules to base-pair with more than one codon
What is the role of aminoacyl-tRNA synthetases in translation?
To attach amino acids to tRNA molecules
What is the function of the small ribosome subunit in translation?
To read the mRNA sequence
What is the function of the large ribosome subunit in translation?
To catalyze the formation of peptide bonds
True or false: The large and small ribosome subunits are normally separated in the cytoplasm until they are used for translation.
False
What is the first modification to occur in eukaryotes during mRNA processing?
5´-methylguanosine cap addition
What is the role of Met-tRNA in translation?
It binds to both large and small ribosomal subunits to initiate translation
What is the process of preventing the translation of mRNA with no 5´-cap?
Nonsense-mediated mRNA decay
What is the role of release factor in translation?
It facilitates termination of translation
What is the function of the wobble base in tRNA molecules?
It allows each type of tRNA molecule to attach to one type of amino acid
What is the role of molecular chaperones in protein folding?
They guide the folding of the nascent polypeptide into its final functional form
What is spliced together during mRNA processing?
Exons
Which of the following is true about the elongation step of translation?
Each type of tRNA molecule can only attach to one type of amino acid
Which of the following is true about the termination step of translation?
The termination step occurs when a stop codon is reached.
Which of the following is true about the initiation step of translation in prokaryotes?
Prokaryotic mRNAs are often polycistronic.
What is the role of elongation factors in translation?
Elongation factors recruit charged tRNA to the A site and improve the accuracy of translation.
What is the function of the wobble base in tRNA molecules?
The wobble base allows flexibility in base pairing between the tRNA anticodon and mRNA codon.
Which of the following is true about polyribosome complexes?
Polyribosome complexes consist of an mRNA molecule and two or more ribosomes.
Why are inhibitors of prokaryotic protein synthesis useful as antibiotics?
Inhibitors of prokaryotic protein synthesis target bacterial ribosomes and have low toxicity to humans.
Which of the following is true about the role of release factors in translation?
Release factors cleave the amino acid from the tRNA and cause ribosome subunits to dissociate.
Study Notes
Gene Expression and Translation
- The final product of gene expression is a protein.
- The main function of translation is to synthesize a polypeptide chain from a sequence of nucleotides in mRNA.
The Genetic Code
- The genetic code is a set of rules that translates a sequence of nucleotides into a sequence of amino acids.
- The genetic code is degenerate, meaning that more than one codon can code for the same amino acid.
Translation Machinery
- Ribosomes are responsible for translating mRNA into a polypeptide chain.
- The small ribosome subunit binds to mRNA, while the large ribosome subunit binds to tRNA.
- Ribosomes play a central role in the initiation, elongation, and termination steps of translation.
- Aminoacyl-tRNA synthetases are enzymes that attach amino acids to tRNA molecules.
- The wobble base in tRNA molecules allows for flexibility in the recognition of codons during translation.
Initiation of Translation
- The initiation of translation requires the binding of mRNA to the small ribosome subunit.
- In prokaryotes, the initiation of translation occurs when the 30S ribosomal subunit binds to the Shine-Dalgarno sequence on mRNA.
- In eukaryotes, the initiation of translation occurs when the 40S ribosomal subunit binds to the 5´-cap of mRNA.
Elongation and Termination
- During elongation, amino acids are added to the growing polypeptide chain through the formation of peptide bonds.
- The elongation step of translation requires the activity of elongation factors.
- The termination of translation occurs when a stop codon is reached, and the polypeptide chain is released from the ribosome.
- Release factors are proteins that recognize stop codons and terminate translation.
mRNA Processing
- In eukaryotes, mRNA is modified through splicing, capping, and polyadenylation before it is translated.
- The first modification to occur in eukaryotes during mRNA processing is the addition of a 5´-cap.
- The 5´-cap is required for the translation of mRNA.
Inhibitors of Protein Synthesis
- Inhibitors of prokaryotic protein synthesis are useful as antibiotics because they can selectively target bacterial ribosomes.
- These inhibitors can prevent the translation of mRNA, thereby inhibiting bacterial growth.
Test your knowledge on RNA-binding sites in the ribosome and the process of translation with this quiz. Explore the functions of the E, P, and A sites, the mRNA binding site, and the role of tRNA molecules in the process.
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