Biology
Protein Synthesis
Protein synthesis is the process by which cells translate DNA into functional proteins. It has two main stages: transcription (DNA → mRNA, in the nucleus) and translation (mRNA → protein, at the ribosome). The genetic code maps every 3-nucleotide codon to one of 20 amino acids.
How to Approach Protein Synthesis
Transcription
RNA polymerase reads the DNA template strand and builds a complementary mRNA. After transcription, the mRNA is processed: 5' cap, poly-A tail, and introns are spliced out. The mature mRNA leaves the nucleus.
Translation initiation
The ribosome assembles around the mRNA at the start codon (AUG). The first tRNA — carrying methionine — binds. The two ribosomal subunits clamp together. The chain is ready to grow.
Translation elongation & termination
tRNAs bring amino acids one by one, matching their anticodons to mRNA codons. Peptide bonds form between adjacent amino acids. At a stop codon (UAA, UAG, UGA), the protein releases and the ribosome dissociates.
Frequently Asked Questions
Why are codons 3 letters?+
Because 4 RNA bases in groups of 3 give 64 combinations — more than enough to code for 20 amino acids plus 3 stop signals. Groups of 2 (16 combinations) would be too few; groups of 4 (256) would be wasteful.
What's the difference between transcription and translation?+
Transcription: DNA → RNA (in the nucleus). Translation: RNA → protein (at the ribosome). They're sequential — translation can only happen after transcription has produced mRNA.
What if there's an error in translation?+
Most are caught by proofreading. Errors that slip through can produce non-functional or harmful proteins — often linked to disease. Cells have quality-control systems (e.g. nonsense-mediated decay) that destroy aberrant mRNAs.
Related Topics
More step-by-step guides in Biology and adjacent subjects.
Stuck on a Protein Synthesis problem?
Snap a photo or type the question. ScanSolve walks you through every step — same as the worked examples above. 5 free solves per day, no card required.