Bacteria translate mRNA as it's made. Eukaryotes wait.
- The idea
- Predict
- See it
- Why
- Check
The idea
“Bacteria cap, tail and splice mRNA like our cells do, or eukaryotes translate it as it's made.”
You learn transcription, processing and translation as one story. Bacteria have no nucleus, and they skip the middle step.
The short version
The mistake: Bacteria cap, tail and splice mRNA like our cells do, or eukaryotes translate it as it's made.
What's actually true: Bacteria translate mRNA as it's made. Eukaryotes cap, tail and splice it in the nucleus, then translate it in the cytoplasm.
- With no nucleus, a bacterium's DNA and ribosomes share the cytoplasm, so translation can start during transcription.
- Bacterial genes usually have no introns, and bacteria have no spliceosome, the complex that cuts introns out.
- In eukaryotes, the nuclear envelope keeps ribosomes away. Pre-mRNA is capped, tailed and spliced in the nucleus, then exported.
- So to make a human protein in bacteria, you use cDNA, an intron-free copy made from mRNA.
On the exam: Bacteria translate mRNA as it's made. Eukaryotes cap, tail and splice it in the nucleus first.