Translation of RNA to Protein Practice Flashcards

Vocabulary-style flashcards covering the translation process, the genetic code, tRNA, ribosomes, and protein regulation based on Chapter 7 and 8 of Essential Cell Biology.

Genetic Code

The rules by which the nucleotide sequence of an mRNA is translated into the amino acid sequence of a protein.

Codons

Sets of $3$ nucleotides in an mRNA sequence that are decoded to specify a particular amino acid.

5'-terminal nucleotide

The nucleotide position typically written to the left when expressing a codon.

Stop Codons

Three specific codons ($UAA$, $UAG$, $UGA$) that do not specify an amino acid but act as termination sites for translation.

tRNA (transfer RNA)

Molecular adaptors that link amino acids to codons in mRNA.

Anticodon

A set of three consecutive nucleotides in a tRNA molecule that binds to a complementary mRNA codon.

3' end of tRNA

The specific end of the tRNA molecule where the matching amino acid is attached.

Pseudouridine ($\psi$)

An unusual base in tRNA derived from uracil by chemical modification after synthesis.

Dihydrouridine ($D$)

An unusual base found in tRNAs that is derived from uracil.

Reading Frames

The three possible ways an mRNA molecule can be translated, depending on where the decoding process begins.

Charging

The process where a specific synthetase enzyme couples a particular amino acid to its corresponding tRNAs.

Aminoacyl-tRNA Synthetase

Specific enzymes responsible for coupling tRNAs to the correct amino acid.

Ribosome

The cytoplasmic organelle where the mRNA message is decoded and translated into protein.

Large Subunit ($60S$)

One of the two components of a eukaryotic ribosome, specifically the larger of the two.

Small Subunit ($40S$)

The smaller component of the eukaryotic ribosome that matches tRNAs to codons.

A site

The binding site on a ribosome for aminoacyl-tRNA.

P site

The binding site on a ribosome for peptidyl-tRNA.

E site

The exit site on a ribosome where spent tRNAs are released.

Translation Step $1$

Binding of a newly charged tRNA to the A site of the ribosome.

Translation Step $2$

The formation of a new peptide bond between the amino acid on the tRNA in the A site and the growing polypeptide chain.

Translation Step $3$

Translocation of the large ribosomal subunit relative to the small subunit.

Translation Step $4$

Translocation of the small ribosomal subunit and ejection of the spent tRNA from the E site.

Release Factor

A protein that binds to the A site when a stop codon is reached, halting translation.

Ribosome Dissociation

The final stage of translation termination where the ribosome components separate from the mRNA.

Translation Initiation Factors ($eIF1-3$)

Proteins required in eukaryotes to properly start the process of protein synthesis.

Initiator tRNA

A special tRNA ($Met-tRNA_{i}$) that carries methionyl and is required to start translation.

Operons

Clusters of genes in prokaryotes that are transcribed together into a single mRNA molecule.

Ribosome-binding sites

Specific sequences (e.g., Shine-Dalgarno) located in the interior of prokaryotic mRNA where ribosomes initiate translation.

Polyribosomes

Also known as polysomes, these consist of a series of ribosomes simultaneously translating the same mRNA molecule.

PABPI (Poly-A Binding Protein)

A protein that binds to the $3'$ poly-A tail and loops eukaryotic mRNA into a circular shape during translation.

Proteasome

An organelle lined with proteases that degrades proteins marked by a polyubiquitin chain.

Proteases

Enzymes inside proteasomes that chop proteins into small pieces.

Polyubiquitin Chain

A chemical marker attached to proteins to signal their degradation by the proteasome.

Post-translational Modifications

Processes including folding, binding cofactors, or covalent changes required for a completed polypeptide to become functional.

Phosphorylation

A type of covalent modification that many proteins require to become active after translation.

Glycosylation

A common post-translational covalent modification involving the addition of sugar groups.

Tetracycline

An antibiotic that blocks the binding of aminoacyl-tRNA to the A site of the bacterial ribosome.

Streptomycin

An antibiotic that prevents the transition from initiation complex to chain elongation and causes miscoding.

Chloramphenicol

An antibiotic that blocks the peptidyl transferase reaction on bacterial ribosomes.

Cycloheximide

An antibiotic that blocks the translocation step in translation.

Rifamycin

An antibiotic that blocks the initiation of transcription by inhibiting RNA polymerase.

RNA World Hypothesis

The theory that life on Earth began with a simple RNA molecule capable of self-replication.

Autocatalysis

The ability of a molecule to catalyze chemical reactions, including its own replication, essential for life's origins.

Ribozyme

An RNA molecule that possesses catalytic activity, such as the ribosome.

Viroids

Large RNA genomes where ribozymes are commonly found.

5' Capping

A modification of eukaryotic pre-mRNA involving the addition of a cap at the $5'$ end.

RNA Splicing

The process in eukaryotes where introns are removed and exons are joined together.

3' Polyadenylation

The addition of a poly-A tail to the $3'$ end of eukaryotic mRNA.

Introns

Non-coding sequences within a eukaryotic gene that are removed during splicing.

Exons

The coding sequences of a eukaryotic gene that remain after RNA splicing.

Pre-mRNA

The primary RNA transcript in eukaryotes before it undergoes capping, splicing, and polyadenylation.

Export

The movement of mature mRNA from the nucleus to the cytoplasm in eukaryotic cells.

Nucleus

The location in eukaryotic cells where transcription, splicing, and polyadenylation occur.

Cytoplasm

The location in eukaryotic cells where translation of mRNA into protein takes place.

Redundancy of Genetic Code

The feature where most amino acids are represented by more than one codon.

Codon First and Second Positions

The two positions within codons that tend to contain the same nucleotides for the same amino acid.

Uracil Chemical Modification

The process that produces unusual bases like $\psi$ and $D$ in tRNA molecules after synthesis.

Free Ribosomes

Ribosomes located unattached within the cytoplasm of eukaryotic cells.

Membrane-attached Ribosomes

Ribosomes attached to the membranes of the endoplasmic reticulum.

Peptidyl-tRNA

The tRNA molecule that holds the growing polypeptide chain during translation.

Aminoacyl-tRNA

A tRNA molecule charged with a single amino acid, which enters the A site.

Polypeptide Chain

The growing sequence of amino acids produced during the translation cycle.

Peptidyl Transferase Reaction

The chemical reaction that joins amino acids together, occurring during Step $2$ of translation.

3' UTR

The untranslated region at the $3'$ end of an mRNA sequence following the stop codon.

Protein production regulation

The control of protein concentrations in a cell via synthesis and degradation.

Three-dimensional Conformation

The specific folded shape a polypeptide must achieve to become a functional protein.

Cofactors

Non-protein molecules that some proteins must bind to after translation to become functional.

Covalent Modifications

Chemical changes, of which there are more than $100$ types, that modify protein activity post-translation.

Prokaryotic Protein Synthesis Inhibitors

Chemicals often used as antibiotics because they target bacterial ribosomes rather than eukaryotic ones.

RNA predating DNA

The evolutionary concept that RNA was the primary genetic material before DNA evolved.

Shine-Dalgarno Sequence

A specific ribosome-binding site sequence found in prokaryotic mRNA.

16S rRNA

The component of the small ($30S$) prokaryotic ribosomal subunit that interacts with the Shine-Dalgarno sequence.

1540 Nucleotides

The length of the $16S$ rDNA in Escherichia coli.

30S Subunit

The small ribosomal subunit specifically found in prokaryotes.

Prokaryotic Polycistronic mRNA

A single prokaryotic mRNA molecule that can encode several different proteins (protein $\alpha$, $\beta$, and $\gamma$).

Initiation Codon

The specific codon ($AUG$) where the ribosome begins translating the coding sequence.

Coding Sequence

The portion of mRNA between the initiation codon and the stop codon that specifies the protein.

Ejected tRNA

A tRNA that is released from the ribosome E site during Step $4$ of translation.

Methionyl-tRNA

The specific amino acid-tRNA complex that serves as the initiator for translation.

Degradation Control

The regulation of the amount of a specific protein in a cell through controlled breakdown.