Bacteria can pick up genes from other species
- The idea
- Predict
- See it
- Why
- Check
The idea
“A cell can only get a gene from its parent, so a gene stays in one family line.”
Every family tree you've drawn has genes flowing down from parent to child. Bacteria also hand DNA to their neighbors.
The short version
The mistake: A cell can only get a gene from its parent, so a gene stays in one family line.
What's actually true: Horizontal gene transfer moves genes between cells that aren't parent and offspring, even across species.
- Passing genes from parent to offspring is called vertical transfer. Any other route is horizontal gene transfer.
- Bacteria do it three ways. Conjugation passes a plasmid between cells joined by a pilus. Transformation takes up loose DNA. Transduction uses a virus.
- Resistance genes spread fast this way. One gene can reach several species, and the drug selects cells that got it.
- So a gene's tree can disagree with the species tree. Bacterial species trees are usually built from rRNA genes because those rarely transfer.
On the exam: A nearly identical gene in distant species points to horizontal transfer.