Translation
60 flashcards covering Translation for the MCAT Biology & Biochemistry section.
Translation is the cellular process that converts the genetic code carried by messenger RNA (mRNA) into a chain of amino acids, forming proteins. This happens in the ribosome, where transfer RNA (tRNA) molecules match specific codons on the mRNA to their corresponding amino acids. It's a crucial step in gene expression, ensuring that the instructions from DNA are turned into functional proteins that drive everything from enzyme activity to cell structure. Without accurate translation, cells couldn't produce the proteins needed for life, making it a foundational concept in biology.
On the MCAT, translation appears in Biology and Biochemistry questions that test your understanding of its steps—initiation, elongation, and termination—as well as key components like ribosomes, tRNA, and mRNA. Expect multiple-choice questions on differences between prokaryotic and eukaryotic translation, common inhibitors, or errors like frameshifts. A frequent trap is confusing translation with transcription, so focus on the specifics of protein synthesis and how mutations affect outcomes to avoid missteps.
Practice drawing the translation process to visualize the steps.
Terms (60)
- 01
Translation
Translation is the process in which the genetic code carried by messenger RNA (mRNA) is decoded by ribosomes to synthesize a specific sequence of amino acids into a polypeptide chain.
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Ribosome
A ribosome is a cellular structure composed of ribosomal RNA and proteins that serves as the site for protein synthesis by linking amino acids together based on mRNA instructions.
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mRNA
Messenger RNA is a single-stranded RNA molecule that carries the genetic information copied from DNA in the form of codons, which specify the sequence of amino acids during translation.
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tRNA
Transfer RNA is a type of RNA that delivers specific amino acids to the ribosome during translation by matching its anticodon to the corresponding mRNA codon.
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Aminoacyl-tRNA synthetase
Aminoacyl-tRNA synthetase is an enzyme that attaches the correct amino acid to its corresponding tRNA molecule, ensuring the accuracy of amino acid selection in translation.
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Codon
A codon is a sequence of three nucleotides in mRNA that specifies a particular amino acid or signals the start or stop of protein synthesis during translation.
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Anticodon
An anticodon is a three-nucleotide sequence on tRNA that base-pairs with a complementary mRNA codon, allowing the correct amino acid to be added to the growing polypeptide chain.
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Start codon
The start codon is the mRNA sequence AUG that initiates translation by signaling the ribosome to begin protein synthesis and codes for the amino acid methionine.
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Stop codon
A stop codon is one of three mRNA sequences—UAA, UAG, or UGA—that signals the end of translation, causing the ribosome to release the completed polypeptide chain.
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Initiation of translation
Initiation of translation is the first stage where the small ribosomal subunit binds to mRNA at the start codon, followed by the large subunit joining to form a complete ribosome ready for elongation.
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Elongation of translation
Elongation of translation is the phase where the ribosome moves along mRNA, adding amino acids one by one to the growing polypeptide chain by matching tRNA anticodons to mRNA codons.
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Termination of translation
Termination of translation occurs when a stop codon is reached, prompting release factors to bind to the ribosome and cause the release of the finished polypeptide chain.
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Peptidyl transferase
Peptidyl transferase is the ribosomal enzyme activity that catalyzes the formation of peptide bonds between amino acids during the elongation phase of translation.
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A site
The A site, or aminoacyl site, on the ribosome is where incoming tRNA molecules carrying amino acids bind before being added to the growing polypeptide chain.
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P site
The P site, or peptidyl site, on the ribosome holds the tRNA attached to the growing polypeptide chain, allowing the transfer of the chain to the incoming amino acid.
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E site
The E site, or exit site, on the ribosome is where the tRNA, after releasing its amino acid, is positioned before exiting the ribosome.
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Shine-Dalgarno sequence
The Shine-Dalgarno sequence is a ribosomal binding site in prokaryotic mRNA that helps position the ribosome correctly at the start codon during translation initiation.
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Kozak sequence
The Kozak sequence is a consensus sequence in eukaryotic mRNA that surrounds the start codon and enhances the efficiency and accuracy of translation initiation.
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Initiation factors
Initiation factors are proteins that assist in the assembly of the ribosomal complex on mRNA during the initiation phase of translation, ensuring proper start codon recognition.
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Elongation factors
Elongation factors are proteins that facilitate the movement of the ribosome along mRNA and the addition of amino acids during the elongation phase of translation.
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Release factors
Release factors are proteins that recognize stop codons on mRNA and trigger the termination of translation by causing the ribosome to release the polypeptide chain.
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Polysome
A polysome, or polyribosome, is a complex of multiple ribosomes simultaneously translating a single mRNA molecule, allowing for efficient production of multiple protein copies.
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Post-translational modification
Post-translational modification refers to chemical changes made to a polypeptide chain after translation, such as phosphorylation or glycosylation, to activate or alter its function.
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Signal recognition particle
The signal recognition particle is a complex that targets proteins destined for the endoplasmic reticulum by binding to their signal sequences during translation.
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Nonsense mutation
A nonsense mutation is a change in DNA that creates a premature stop codon in mRNA, leading to a truncated, often nonfunctional protein during translation.
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Missense mutation
A missense mutation is a DNA change that alters a codon to specify a different amino acid, potentially affecting the protein's structure and function during translation.
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Frameshift mutation
A frameshift mutation is an insertion or deletion of nucleotides not in multiples of three, which shifts the reading frame of mRNA and alters the resulting protein sequence.
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Wobble hypothesis
The wobble hypothesis explains how a single tRNA can recognize multiple codons for the same amino acid due to flexibility in the third base pairing during translation.
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Genetic code universality
The genetic code is nearly universal across organisms, meaning the same codons specify the same amino acids during translation, with few exceptions in mitochondria or certain microbes.
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Reading frame
The reading frame is the way nucleotides in mRNA are grouped into codons starting from the start codon, and any shift can lead to a completely different protein sequence.
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Open reading frame
An open reading frame is a sequence of mRNA from a start codon to a stop codon that has the potential to be translated into a protein without interruptions.
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Translation inhibitors
Translation inhibitors are molecules, such as certain antibiotics, that block specific steps of translation, preventing protein synthesis in bacteria or cells.
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Puromycin
Puromycin is an antibiotic that mimics tRNA and causes premature chain termination during translation by being incorporated into the growing polypeptide.
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Tetracycline
Tetracycline is an antibiotic that inhibits translation by binding to the ribosome and preventing the attachment of aminoacyl-tRNA to the A site.
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Chloramphenicol
Chloramphenicol is an antibiotic that blocks peptidyl transferase activity on the ribosome, halting peptide bond formation during translation.
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Energy requirements for translation
Translation requires energy in the form of GTP hydrolysis to drive steps like tRNA binding and ribosome translocation along mRNA.
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Role of GTP in translation
GTP provides the energy for key processes in translation, such as the binding of initiation and elongation factors to the ribosome.
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Fidelity of translation
Fidelity of translation refers to the accuracy with which mRNA codons are translated into the correct amino acid sequence, maintained by proofreading mechanisms.
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Proofreading in translation
Proofreading in translation involves mechanisms like the rejection of incorrect tRNA molecules by the ribosome to ensure the correct amino acid is added.
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Suppressor tRNA
A suppressor tRNA is a mutated tRNA that can recognize a stop codon and insert an amino acid instead, potentially restoring function in certain genetic mutations.
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Amino acid activation
Amino acid activation is the process where an amino acid is attached to its tRNA with the help of ATP, forming aminoacyl-tRNA for use in translation.
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Charging of tRNA
Charging of tRNA is the enzymatic attachment of the correct amino acid to tRNA, a critical step that ensures specificity in the translation process.
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Degeneracy of the genetic code
Degeneracy of the genetic code means that multiple codons can code for the same amino acid, reducing the impact of mutations on the translated protein.
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Synonymous codons
Synonymous codons are different codons that encode the same amino acid, allowing for variations in mRNA sequences without changing the protein product.
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Non-synonymous codons
Non-synonymous codons are those that, when mutated, result in a different amino acid being incorporated during translation, potentially altering protein function.
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Codon bias
Codon bias is the preference for certain synonymous codons in an organism's genes, which can affect the speed and efficiency of translation.
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Translational efficiency
Translational efficiency is the rate at which mRNA is translated into protein, influenced by factors like codon usage and mRNA secondary structure.
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Ribosomal RNA (rRNA)
Ribosomal RNA is a component of ribosomes that provides the structural framework and catalyzes peptide bond formation during translation.
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Small ribosomal subunit
The small ribosomal subunit binds to mRNA and ensures the correct reading frame during the initiation of translation.
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Large ribosomal subunit
The large ribosomal subunit contains the peptidyl transferase center and facilitates the elongation and termination steps of translation.
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Prokaryotic vs. eukaryotic ribosomes
Prokaryotic ribosomes are 70S and lack a nucleus, while eukaryotic ribosomes are 80S and occur in the cytoplasm, affecting the initiation and regulation of translation.
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Eukaryotic translation initiation complex
The eukaryotic translation initiation complex is a multi-protein assembly that scans mRNA for the start codon to begin translation.
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Cap-dependent translation
Cap-dependent translation in eukaryotes requires the 5' cap of mRNA for ribosome binding and initiation, making it the primary mechanism for most cellular proteins.
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IRES
IRES, or internal ribosome entry site, is a sequence in some mRNAs that allows ribosomes to initiate translation without the 5' cap, often in viral RNAs.
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MicroRNAs and translation regulation
MicroRNAs are small RNAs that bind to mRNA and inhibit translation by preventing ribosome binding or causing mRNA degradation.
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siRNAs and translation
Small interfering RNAs silence gene expression by targeting mRNA for degradation or blocking translation, often as part of RNA interference pathways.
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Translational repression
Translational repression is a regulatory mechanism where proteins or RNAs bind to mRNA to prevent its translation into protein.
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Polyribosome
Polyribosome is another term for polysome, where multiple ribosomes translate a single mRNA to produce proteins efficiently.
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Nascent polypeptide chain
A nascent polypeptide chain is the growing protein being synthesized on the ribosome during translation before it is fully completed.
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Exit tunnel in ribosome
The exit tunnel in the ribosome is the channel through which the newly synthesized polypeptide chain emerges as translation proceeds.