Specialized cells keep their genes and switch most off
- The idea
- Predict
- See it
- Why
- Check
The idea
“Cells specialize by losing genes they don't need, so liver and nerve cells have different genes.”
Liver and nerve cells look nothing alike, so it's easy to assume they have different genes.
The short version
The mistake: Cells specialize by losing genes they don't need, so liver and nerve cells have different genes.
What's actually true: Almost every cell in your body has the same genes. Cell types differ in which of those genes they transcribe.
- Every cell in your body came from one fertilized egg. Mitosis gives each new cell the full genome.
- Cell types differ in gene expression, meaning which genes get transcribed into mRNA and made into protein.
- Transcription factors decide. They bind promoters and enhancers and turn genes on or off.
- Red blood cells are a rare exception. They lose their nucleus.
On the exam: Different cells, same genes. Ask which genes are switched on.