Transcription and Translation: From DNA to Protein Explained
By Dr. Zubair Khalid, DVM, MS, PhD ·

Gene expression is the process by which the information encoded in a gene is converted into a functional product, typically a protein. This process occurs in two main steps: transcription and translation. Transcription is the synthesis of an RNA molecule from a DNA template, while translation is the synthesis of a polypeptide chain from an mRNA template. Together, these processes constitute the flow of genetic information from DNA to RNA to protein, a framework known as the central dogma of molecular biology.
For an undergraduate student, mastering transcription and translation is foundational. These processes explain how genotype gives rise to phenotype, how mutations exert their effects, and how cells respond to environmental signals. This article provides a comprehensive, mechanistic overview of both processes, their regulation, and the experimental methods used to study them.
Introduction to Transcription and Translation
Central Dogma of Molecular Biology
The central dogma, first articulated by Francis Crick in 1957, describes the directional flow of genetic information: DNA → RNA → protein. DNA serves as the stable repository of genetic information. During transcription, a segment of DNA is copied into messenger RNA (mRNA). During translation, the mRNA sequence is decoded by the ribosome to produce a specific amino acid sequence.
This flow is not entirely unidirectional in all organisms. Retroviruses, such as HIV, carry an enzyme called reverse transcriptase that synthesizes DNA from an RNA template. However, for the vast majority of cellular life, the DNA → RNA → protein pathway is the primary route of gene expression. The central dogma also recognizes that RNA can be replicated in some viruses, and that proteins are never used as templates for nucleic acid synthesis.
Why Transcription and Translation Matter
Transcription and translation are the molecular basis of phenotype. Every trait—from eye color to enzyme activity—ultimately depends on which proteins are produced, in what quantity, and at what time. Mutations in DNA can alter transcription (e.g., by disrupting promoter sequences) or translation (e.g., by creating premature stop codons), leading to disease. Moreover, many antibiotics target bacterial transcription and translation specifically because these processes differ sufficiently between prokaryotes and eukaryotes. Rifampicin inhibits bacterial RNA polymerase, while cycloheximide blocks eukaryotic ribosomes—both are clinically useful because of these differences.
Understanding these processes also underpins modern biotechnology. Recombinant protein production, gene therapy, CRISPR-based gene editing, and mRNA vaccines all rely on a detailed knowledge of transcription and translation. For example, the Pfizer-BioNTech and Moderna COVID-19 vaccines deliver mRNA that is translated by host ribosomes to produce the SARS-CoV-2 spike protein, eliciting an immune response.
Transcription: DNA to RNA
Transcription is catalyzed by the enzyme RNA polymerase, which synthesizes an RNA strand complementary to the DNA template strand. The process occurs in three phases: initiation, elongation, and termination. The key features of transcription are its directionality (always 5′ to 3′), its use of ribonucleotide triphosphates (ATP, GTP, CTP, UTP) as substrates, and its requirement for a DNA template but not a primer.
Initiation: Promoters and Transcription Factors
Transcription initiation begins when RNA polymerase binds to a specific DNA sequence called a promoter. In bacteria, the promoter contains two conserved sequence elements: the −10 box (TATAAT, also called the Pribnow box) and the −35 box (TTGACA), located 10 and 35 base pairs upstream of the transcription start site, respectively. The sigma (σ) factor, a subunit of bacterial RNA polymerase, recognizes these sequences and positions the enzyme at the start site. The holoenzyme (core enzyme + σ factor) then unwinds approximately 13 base pairs of DNA to form an open complex, and the first ribonucleotide is incorporated.
In eukaryotes, the process is more complex. Three RNA polymerases exist: RNA polymerase I (transcribes rRNA), RNA polymerase II (transcribes mRNA and some noncoding RNAs), and RNA polymerase III (transcribes tRNA and 5S rRNA). For mRNA transcription, RNA polymerase II requires the assembly of general transcription factors (GTFs) at the promoter. The first step is binding of TFIID, which contains the TATA-binding protein (TBP), to the TATA box, a conserved sequence typically located about 25–30 base pairs upstream of the start site. This is followed by recruitment of TFIIA, TFIIB, TFIIF, TFIIE, and TFIIH. TFIIH has helicase activity that unwinds the DNA, and its kinase activity phosphorylates the C-terminal domain (CTD) of RNA polymerase II, triggering promoter escape. The TATA box transcription is a critical regulatory element, and mutations within it can drastically reduce transcription levels. For a detailed walkthrough of the steps involved, see Transcription Initiation.
Elongation: RNA Synthesis
During elongation, RNA polymerase moves along the template strand in the 3′ to 5′ direction, synthesizing RNA in the 5′ to 3′ direction. The enzyme maintains a transcription bubble of approximately 17–20 base pairs of unwound DNA. As the polymerase advances, it adds ribonucleotides complementary to the template strand: A pairs with U (not T), T pairs with A, C pairs with G, and G pairs with C. The growing RNA chain remains base-paired to the template DNA over a short region (about 8–9 base pairs) before being displaced as the DNA re-anneals behind the polymerase.
Elongation is not a uniform process. RNA polymerase can pause, and these pauses are often regulatory. In eukaryotes, the CTD of RNA polymerase II is phosphorylated at different serine residues (Ser5 during initiation, Ser2 during elongation), which recruits different processing factors. Elongation factors such as TFIIS rescue stalled polymerases by stimulating the intrinsic cleavage activity of the enzyme, allowing it to backtrack and resume synthesis. The overall elongation rate in bacteria is approximately 40–80 nucleotides per second, while in eukaryotes it is slower, around 20–30 nucleotides per second.
Termination: Stop Signals
Termination signals differ between prokaryotes and eukaryotes. In bacteria, two main mechanisms exist. Rho-dependent termination requires the Rho protein, a hexameric helicase that binds to a C-rich region on the nascent RNA and translocates toward the polymerase, causing it to dissociate. Rho-independent termination (also called intrinsic termination) relies on a hairpin loop formed by a GC-rich palindromic sequence in the RNA, followed by a run of U residues. The hairpin destabilizes the RNA–DNA hybrid, and the weak A-U base pairs facilitate dissociation.
In eukaryotes, termination of RNA polymerase II transcription is coupled to mRNA processing. The cleavage and polyadenylation specificity factor (CPSF) recognizes the polyadenylation signal AAUAAA in the nascent RNA, while cleavage stimulatory factor (CstF) binds a downstream U/GU-rich element. These factors cleave the RNA, and the polymerase continues transcribing for a short distance before being released by a mechanism involving the exonuclease XRN2, which degrades the remaining RNA and "torpedoes" the polymerase off the DNA. For more detail on the various mechanisms, see Transcription Termination and Transcription Stop.
RNA Processing in Eukaryotes
In eukaryotes, the primary transcript (pre-mRNA) undergoes extensive processing before it is exported to the cytoplasm for translation. These modifications are essential for mRNA stability, nuclear export, and efficient translation.
5' Capping and 3' Polyadenylation
The 5′ cap is added co-transcriptionally, when the nascent RNA is only about 20–30 nucleotides long. A 7-methylguanosine cap is linked to the first nucleotide via a 5′–5′ triphosphate bridge. This cap structure (m7GpppN) is recognized by the cap-binding complex (CBC), which promotes nuclear export and protects the mRNA from 5′→3′ exonucleases. The cap also plays a critical role in translation initiation, as it is bound by eukaryotic initiation factor 4E (eIF4E).
At the 3′ end, the pre-mRNA is cleaved downstream of the polyadenylation signal and a poly(A) tail of 200–250 adenine residues is added by poly(A) polymerase. This tail is bound by poly(A)-binding proteins (PABPs), which protect the mRNA from degradation and enhance translation initiation. The poly(A) tail also plays a role in translational regulation; its length can be modulated in the cytoplasm to control protein production.
RNA Splicing and Alternative Splicing
Most eukaryotic genes contain introns (noncoding sequences) that must be removed from the pre-mRNA, while exons (coding sequences) are joined together. This process, called splicing, is catalyzed by the spliceosome, a large ribonucleoprotein complex composed of five small nuclear RNAs (snRNAs: U1, U2, U4, U5, U6) and associated proteins. The spliceosome recognizes conserved sequences at the 5′ splice site (GU), the 3′ splice site (AG), and the branch point (A), and performs two transesterification reactions to excise the intron and ligate the exons.
Alternative splicing allows a single gene to produce multiple mRNA isoforms by selecting different combinations of exons. This greatly expands the coding capacity of the genome; it is estimated that over 95% of human multi-exon genes undergo alternative splicing. For example, the DSCAM gene in Drosophila can generate over 38,000 different mRNA isoforms through alternative splicing. Splicing is regulated by splicing enhancers and silencers, which are bound by serine/arginine-rich (SR) proteins and heterogeneous nuclear ribonucleoproteins (hnRNPs), respectively.
Translation: RNA to Protein
Translation is the process by which the sequence of an mRNA is decoded into a polypeptide chain. It occurs on ribosomes, which are large ribonucleoprotein complexes composed of a small subunit (which decodes the mRNA) and a large subunit (which catalyzes peptide bond formation). Transfer RNA (tRNA) molecules serve as adaptors, carrying specific amino acids and recognizing specific codons on the mRNA.
The Genetic Code and Codons
The genetic code is a set of rules that maps each three-nucleotide sequence (codon) to a specific amino acid or a stop signal. With four nucleotides, there are 64 possible codons: 61 encode amino acids, and 3 are stop codons (UAA, UAG, UGA). The code is degenerate—most amino acids are encoded by more than one codon. For example, leucine is encoded by six codons (UUA, UUG, CUU, CUC, CUA, CUG), while tryptophan is encoded by only one (UGG). The code is nearly universal, with minor exceptions in mitochondria and some ciliates.
The codon is read on the mRNA in the 5′ to 3′ direction. The start codon is almost always AUG, which encodes methionine. In bacteria, the initiator tRNA carries a modified methionine (formylmethionine, fMet), while in eukaryotes, the initiator tRNA carries unmodified methionine.
Initiation: Ribosome Assembly
Translation initiation is the rate-limiting step of translation and is highly regulated. In eukaryotes, initiation begins with the formation of the 43S preinitiation complex: the 40S ribosomal subunit binds eIF2-GTP-Met-tRNAi, along with eIF1, eIF1A, eIF3, and eIF5. This complex is recruited to the 5′ cap of the mRNA via eIF4F (composed of eIF4E, eIF4A, and eIF4G). The complex then scans the mRNA in the 5′ to 3′ direction until it encounters the first AUG codon in a favorable context (the Kozak consensus sequence: GCCRCCAUGG). At this point, eIF2 hydrolyzes GTP, the 60S subunit joins, and all initiation factors are released, forming the 80S initiation complex.
In bacteria, initiation is simpler. The 30S subunit binds the Shine-Dalgarno sequence (AGGAGG), located 6–10 nucleotides upstream of the start codon, via base-pairing with the anti-Shine-Dalgarno sequence at the 3′ end of 16S rRNA. The initiator tRNA (fMet-tRNAfMet) binds directly to the P site, and the 50S subunit joins to form the 70S ribosome.
Elongation: Peptide Bond Formation
Elongation proceeds in three steps: codon recognition, peptide bond formation, and translocation. The ribosome has three tRNA binding sites: the A (aminoacyl) site, the P (peptidyl) site, and the E (exit) site.
- Codon recognition: The elongation factor eEF1A (in eukaryotes) or EF-Tu (in bacteria) delivers an aminoacyl-tRNA to the A site, where its anticodon base-pairs with the mRNA codon. This is a proofreading step; incorrect codon–anticodon pairing is rejected.
- Peptide bond formation: The peptidyl transferase center, located in the large subunit rRNA (23S rRNA in bacteria, 28S rRNA in eukaryotes), catalyzes the transfer of the growing polypeptide chain from the P-site tRNA to the amino group of the A-site aminoacyl-tRNA. This forms a new peptide bond and leaves the A-site tRNA with the growing chain.
- Translocation: The ribosome moves one codon along the mRNA. The deacylated tRNA moves from the P site to the E site and is released, while the peptidyl-tRNA moves from the A site to the P site. This step is catalyzed by eEF2 (eukaryotes) or EF-G (bacteria), which hydrolyzes GTP.
The elongation rate in bacteria is approximately 15–20 amino acids per second; in eukaryotes, it is slower, around 5–10 amino acids per second.
Termination: Stop Codons
Termination occurs when a stop codon (UAA, UAG, or UGA) enters the A site. No tRNA recognizes these codons. Instead, release factors bind. In eukaryotes, eRF1 recognizes all three stop codons and, together with eRF3, promotes hydrolysis of the peptidyl-tRNA bond, releasing the completed polypeptide. In bacteria, RF1 recognizes UAA and UAG, RF2 recognizes UAA and UGA, and RF3 facilitates their release. The ribosome then dissociates into its subunits, and the mRNA is released. The newly synthesized protein may undergo post-translational modifications, folding, and targeting to its final destination.
Key Differences Between Prokaryotic and Eukaryotic Processes
The fundamental chemistry of transcription and translation is conserved across all domains of life, but there are important differences in location, timing, and machinery.
| Feature | Prokaryotes | Eukaryotes |
|---|---|---|
| Location of transcription | Cytoplasm | Nucleus |
| Location of translation | Cytoplasm (coupled to transcription) | Cytoplasm (on free or ER-bound ribosomes) |
| RNA polymerase | Single enzyme (5 subunits + σ factor) | Three enzymes (Pol I, II, III) |
| Promoter recognition | σ factor | General transcription factors (TFIID, etc.) |
| mRNA processing | None (polycistronic possible) | 5′ cap, poly(A) tail, splicing |
| Ribosome size | 70S (50S + 30S) | 80S (60S + 40S) |
| Initiation of translation | Shine-Dalgarno sequence | 5′ cap scanning, Kozak sequence |
| First amino acid | Formylmethionine (fMet) | Methionine (Met) |
| Coupling of transcription and translation | Yes (simultaneous) | No (spatially separated) |
Coupled vs. Separated Processes
In bacteria, transcription and translation are coupled: ribosomes begin translating the mRNA while RNA polymerase is still synthesizing it. This is possible because both processes occur in the cytoplasm. This coupling allows for rapid responses to environmental changes and enables a process called transcriptional attenuation, where translation of a leader peptide regulates downstream gene expression. In eukaryotes, transcription occurs in the nucleus and translation in the cytoplasm, so the two processes are strictly separated. The mRNA must be processed, exported through nuclear pore complexes, and localized before translation can begin.
Differences in RNA Polymerases and Ribosomes
Prokaryotes have a single RNA polymerase that transcribes all genes, while eukaryotes have three specialized polymerases. Prokaryotic ribosomes are 70S (sedimentation coefficient) and are composed of a 50S large subunit (containing 23S and 5S rRNA) and a 30S small subunit (containing 16S rRNA). Eukaryotic ribosomes are 80S, composed of a 60S large subunit (28S, 5.8S, and 5S rRNA) and a 40S small subunit (18S rRNA). These differences are clinically significant: many antibiotics (e.g., tetracyclines, aminoglycosides, macrolides) specifically target bacterial ribosomes without affecting eukaryotic ribosomes.
Methods Used to Study Transcription and Translation
Several experimental techniques are used to study gene expression at the transcriptional and translational levels.
RNA-Seq and Microarrays
RNA sequencing (RNA-seq) is a high-throughput method for quantifying and characterizing the transcriptome. Total RNA is isolated, converted to cDNA, and sequenced. The resulting reads are aligned to a reference genome to determine gene expression levels, identify splice variants, and detect novel transcripts. RNA-seq can also reveal allele-specific expression and RNA editing events. Microarrays, an older technology, use fluorescently labeled cDNA hybridized to probes on a solid surface to measure expression of known genes. While microarrays are cheaper and faster for targeted analyses, RNA-seq has largely replaced them due to its broader dynamic range and ability to detect novel transcripts.
Ribosome Profiling
Ribosome profiling (Ribo-seq) is a technique that provides a genome-wide snapshot of translation. Cells are treated with cycloheximide to freeze ribosomes on mRNA, and the mRNA fragments protected by ribosomes (ribosome footprints) are isolated, converted to cDNA, and sequenced. The density and position of ribosome footprints reveal which mRNAs are being translated, the translation rate, and the precise positions of ribosomes. This method can identify translation start sites, paused ribosomes, and upstream open reading frames (uORFs) that regulate translation.
Reporter Gene Assays
Reporter assays are used to measure the activity of a promoter or a regulatory element. A reporter gene (e.g., luciferase, green fluorescent protein [GFP], or β-galactosidase) is placed under the control of the promoter of interest, and the resulting protein activity or fluorescence is measured. For example, the firefly luciferase assay involves lysing cells and adding luciferin and ATP; the emitted light is proportional to luciferase activity. This approach is widely used to study the effects of transcription factors, enhancers, and mutations on gene expression. For a visual overview of the process, see Transcription Diagram.
Regulation of Transcription and Translation
Gene expression is regulated at multiple levels, allowing cells to respond to developmental cues, environmental stresses, and metabolic demands.
Transcriptional Regulation
Transcriptional regulation is the primary control point for most genes. In prokaryotes, the lac operon is a classic example. In the absence of lactose, the LacI repressor binds the operator sequence and blocks RNA polymerase. When lactose is present, it is converted to allolactose, which binds LacI and causes it to release the operator, allowing transcription. Additionally, catabolite activator protein (CAP) binds cAMP and activates transcription when glucose is scarce.
In eukaryotes, transcriptional regulation involves sequence-specific DNA-binding proteins called Transcription Factors. These proteins bind enhancers or silencers—DNA elements that can be located thousands of base pairs away from the promoter—and recruit coactivators or corepressors. Coactivators such as p300/CBP have histone acetyltransferase (HAT) activity, which loosens chromatin structure and promotes transcription. Corepressors recruit histone deacetylases (HDACs), which compact chromatin and repress transcription. The combinatorial action of multiple transcription factors at a given promoter integrates signals from multiple pathways.
Translational Regulation
Translational regulation allows for rapid changes in protein production without altering mRNA levels. One major mechanism is the regulation of translation initiation. For example, phosphorylation of eIF2α by kinases such as PKR (activated by double-stranded RNA during viral infection) or PERK (activated by ER stress) reduces the availability of eIF2-GTP-Met-tRNAi, globally inhibiting translation. Conversely, the mTOR pathway regulates translation by phosphorylating eIF4E-binding proteins (4E-BPs), releasing eIF4E to promote cap-dependent translation.
MicroRNAs (miRNAs) are small noncoding RNAs (~22 nucleotides) that regulate translation post-transcriptionally. They are incorporated into the RNA-induced silencing complex (RISC), where they base-pair with complementary sequences in the 3′ untranslated region (UTR) of target mRNAs. This binding typically leads to translational repression and/or mRNA degradation. A single miRNA can regulate hundreds of target mRNAs, making miRNAs powerful regulators of gene expression networks.
Common Mistakes and Misconceptions
Students frequently encounter several conceptual difficulties when learning transcription and translation.
Directionality: 5' to 3'
A common error is confusing the direction of template reading with the direction of product synthesis. Nucleic acids are always synthesized in the 5′ to 3′ direction. The template strand is read in the 3′ to 5′ direction. For example, if the template strand is 3′-TAC-5′, the RNA product will be 5′-AUG-3′. Students often mistakenly write the RNA sequence in the same orientation as the template. Remember: the product is antiparallel and complementary to the template.
Codon vs. Anticodon
The codon is a three-nucleotide sequence on the mRNA, read in the 5′ to 3′ direction. The anticodon is a three-nucleotide sequence on the tRNA, which is antiparallel to the codon. For example, the codon 5′-AUG-3′ pairs with the anticodon 3′-UAC-5′. Students often forget the antiparallel orientation and incorrectly write the anticodon as 5′-UAC-3′. The wobble position (third nucleotide of the codon) allows non-Watson-Crick base pairing, which explains the degeneracy of the genetic code.
Introns vs. Exons
Introns are noncoding sequences that are removed during splicing; exons are coding sequences that are retained in the mature mRNA. Students sometimes confuse these terms or forget that introns are present in the pre-mRNA but absent in the mature mRNA. Additionally, not all exons are translated; untranslated regions (UTRs) at the 5′ and 3′ ends of the mRNA are exonic but do not encode protein.
Another common misconception is that transcription errors are rare. While RNA polymerase has proofreading activity, its error rate is approximately 1 in 10⁴ to 10⁵ nucleotides, which is higher than the DNA polymerase error rate (1 in 10⁹). However, because many RNA copies are made from a single gene, the impact of a single Transcription Error is usually minimal.
Practical Summary: From Gene to Protein
Step-by-Step Overview
- Transcription initiation: RNA polymerase (with σ factor in bacteria, or with GTFs in eukaryotes) binds the promoter and unwinds the DNA.
- Transcription elongation: RNA polymerase synthesizes RNA in the 5′ to 3′ direction, complementary to the template strand.
- Transcription termination: RNA polymerase dissociates at a termination signal (Rho-dependent or intrinsic in bacteria; polyadenylation-coupled in eukaryotes).
- RNA processing (eukaryotes only): The pre-mRNA receives a 5′ cap, a 3′ poly(A) tail, and undergoes splicing to remove introns.
- mRNA export (eukaryotes): The mature mRNA is transported from the nucleus to the cytoplasm.
- Translation initiation: The ribosome assembles on the mRNA at the start codon (AUG).
- Translation elongation: Aminoacyl-tRNAs deliver amino acids to the A site; peptide bonds form; the ribosome translocates.
- Translation termination: A stop codon is recognized by release factors; the polypeptide is released.
- Protein folding and modification: The polypeptide folds into its functional conformation and may undergo post-translational modifications.
Study Tips for Exams
- Draw the process: Sketch a diagram of transcription and translation, labeling the template strand, coding strand, RNA polymerase, ribosome, tRNA, and amino acids. This reinforces spatial relationships.
- Use mnemonics: For the genetic code, remember that the start codon is AUG ("AUG = AUGust, the beginning"). For stop codons, "UAA, UAG, UGA" can be remembered as "U Are Away, U Are Gone, U Go Away."
- Practice with sequences: Given a DNA template sequence, practice writing the mRNA sequence, then the amino acid sequence using a codon table. This is a common exam question.
- Compare and contrast: Make a table comparing prokaryotic and eukaryotic transcription and translation. This helps consolidate differences.
- Understand the logic, not just the facts: Instead of memorizing every factor, understand the function of each component. For example, the 5′ cap is a "tag" for the ribosome; the poly(A) tail is a "stability shield."
Frequently Asked Questions
What is transcription and translation?
Transcription is the process by which an RNA molecule is synthesized from a DNA template, catalyzed by RNA polymerase. Translation is the process by which the sequence of an mRNA is decoded by the ribosome to produce a polypeptide chain. Together, they constitute the two main steps of gene expression, converting the genetic information in DNA into functional proteins.
What are the steps of transcription and translation?
Transcription has three steps: initiation (RNA polymerase binds the promoter and unwinds DNA), elongation (RNA is synthesized in the 5′ to 3′ direction), and termination (RNA polymerase dissociates at a stop signal). Translation also has three steps: initiation (the ribosome assembles on the mRNA at the start codon), elongation (amino acids are added one by one via tRNA), and termination (a stop codon is recognized and the polypeptide is released).
How do transcription and translation differ?
Transcription produces RNA from DNA, occurs in the nucleus (eukaryotes) or cytoplasm (prokaryotes), and uses RNA polymerase. Translation produces protein from mRNA, occurs on ribosomes in the cytoplasm, and uses tRNA and amino acids. Transcription involves base-pairing rules (A-U, T-A, C-G), while translation involves the genetic code (codon to amino acid).
Where does transcription and translation occur in the cell?
In eukaryotes, transcription occurs in the nucleus, and translation occurs in the cytoplasm (either on free ribosomes or on the rough endoplasmic reticulum). In prokaryotes, both processes occur in the cytoplasm, and they are often coupled—ribosomes begin translating an mRNA while it is still being transcribed.
What is the role of mRNA in transcription and translation?
Messenger RNA (mRNA) is the intermediate that carries the genetic information from DNA to the ribosome. During transcription, mRNA is synthesized as a complementary copy of the template DNA strand. During translation, the mRNA sequence is read in codons (triplets) by the ribosome to direct the incorporation of specific amino acids into a polypeptide.
What are common transcription and translation problems?
Common problems include: confusing the template strand with the coding strand; writing RNA sequences in the wrong orientation; forgetting that RNA uses U instead of T; misidentifying introns and exons; and failing to account for the antiparallel nature of codon–anticodon pairing. Students also often forget that transcription and translation are coupled in prokaryotes but not in eukaryotes.
How can I remember the difference between transcription and translation?
A simple mnemonic: "Transcription copies the text (DNA to RNA); Translation translates the text into a different language (RNA to protein)." Another way: transcription is about "transcribing" the genetic message into RNA, while translation is about "translating" the RNA message into the language of amino acids.
Key Takeaways
- Transcription converts DNA into RNA using RNA polymerase; translation converts mRNA into protein using ribosomes, tRNA, and amino acids.
- Both processes occur in three phases: initiation, elongation, and termination.
- In eukaryotes, pre-mRNA undergoes 5′ capping, 3′ polyadenylation, and splicing before translation; in prokaryotes, transcription and translation are coupled in the cytoplasm.
- The genetic code is degenerate, with 61 codons encoding amino acids and 3 stop codons; AUG is the start codon.
- Nucleic acids are always synthesized 5′ to 3′; the template strand is read 3′ to 5′.
- Gene expression is regulated at both transcriptional (promoters, enhancers, transcription factors) and translational (eIF2α phosphorylation, miRNAs) levels.
- Understanding the differences between prokaryotic and eukaryotic machinery is essential for appreciating antibiotic mechanisms and biotechnological applications.
Further Reading
- Blaha GM, Wade JT. Transcription-Translation Coupling in Bacteria. Annual review of genetics. 2022. PubMed 36055649
- Webster MW, Weixlbaumer A. Macromolecular assemblies supporting transcription-translation coupling. Transcription. 2021. PubMed 34570660
- Wang T, Lu Y. Toward Minimal Transcription-Translation Machinery. ACS synthetic biology. 2023. PubMed 37852206
- Chen HZ, Zubay G. Prokaryotic coupled transcription-translation. Methods in enzymology. 1983. PubMed 631034101047-2)
- Qureshi NS, Duss O. Tracking transcription-translation coupling in real time. Nature. 2025. PubMed 39633055
- Wang C et al. Structural basis of transcription-translation coupling. Science (New York, N.Y.). 2020. PubMed 32820061