What is the Central Dogma of Protein Synthesis?
The central dogma of molecular biology describes the flow of genetic information within a cell: DNA is transcribed into RNA, and RNA is translated into protein. Proposed by Francis Crick in 1958, it remains the foundational law explaining how genes become functional molecules.
The central dogma states that genetic information flows in one main direction: DNA → RNA (transcription) → Protein (translation), turning stored genetic code into functional proteins.
- 1↓DNA (Nucleus)The gene's sequence stores the instructions as a double-stranded helix.
- 2↓TranscriptionRNA polymerase copies one DNA strand into a complementary mRNA strand.
- 3↓mRNA Processing & ExportmRNA is capped, spliced, and exported to the cytoplasm.
- 4↓TranslationRibosomes read mRNA codons; tRNA delivers matching amino acids.
- 5ProteinThe amino acid chain folds into a functional protein.
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Step-by-step worked examples
An mRNA coding region has 300 nucleotides. How many amino acids does the protein contain?
Each amino acid is coded by a triplet codon (3 nucleotides) Amino acids = 300 / 3 = 100 One codon is usually a stop codon, so the protein has about 99 amino acids
A DNA template strand reads ATG-CGA-TTT. What protein-coding mRNA is produced, and what does it start with?
Transcription pairs A-U, T-A, C-G, G-C ATG→UAC, CGA→GCU, TTT→AAA mRNA = UAC-GCU-AAA (this example does not start with AUG, so recheck orientation: using the correct template convention, mRNA mirrors the coding strand with T→U) Using the coding (sense) strand ATG-CGA-TTT directly as mRNA sense gives AUG-CGA-UUU, starting with the start codon AUG (methionine)
If a mutation changes one DNA base, how might it affect the final protein?
A point mutation changes one mRNA codon That codon may code for a different amino acid (missense) or a stop signal (nonsense) The protein's shape and function can change, sometimes causing disease
Flashcards
Quick quiz
Q1.What is the correct order of the central dogma?
Q2.What enzyme carries out transcription?
Q3.Where does translation occur?
Q4.How many nucleotides make up one codon?
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Common mistakes
Thinking protein is made directly from DNA. — Correct: DNA is first transcribed into mRNA; the ribosome then translates mRNA into protein.
Believing the central dogma has no exceptions. — Correct: Some viruses (retroviruses) reverse-transcribe RNA back into DNA, an exception to the typical flow.
Confusing transcription and translation. — Correct: Transcription makes RNA from DNA; translation makes protein from RNA.
Assuming every codon codes for an amino acid. — Correct: Some codons are stop codons that end translation without coding for an amino acid.
FAQ
What is the central dogma of molecular biology?
It is the principle describing how genetic information flows from DNA to RNA to protein through transcription and translation.
What is the central dogma formula?
DNA → (transcription) → mRNA → (translation) → Protein describes the standard flow of genetic information.
What are examples of the central dogma in action?
Insulin gene expression, hemoglobin synthesis, and enzyme production in every living cell all follow the DNA to RNA to protein pathway.
How to calculate protein length from mRNA?
Divide the number of coding nucleotides by 3 to get the number of amino acids, since each codon (3 nucleotides) specifies one amino acid.