Same alleles don't always make the same trait
- The idea
- Predict
- See it
- Why
- Check
The idea
“Same alleles mean the same trait, so any difference must come from different alleles.”
Genes do shape traits, so alleles are the natural suspect when two groups differ. The environment a gene is expressed in can change the result too.
The short version
The mistake: Same alleles mean the same trait, so any difference must come from different alleles.
What's actually true: A genotype sets a range of possible traits. The environment an organism develops in helps decide which one it shows.
- Genotype is the alleles you carry. Phenotype is the trait you show. How much protein a cell makes from a gene, and when, can depend on its surroundings.
- Predator chemicals changed the young Daphnia's gene expression as she grew. One genotype showing different phenotypes in different environments is phenotypic plasticity.
- Random splitting spreads alleles evenly on average, so a steady difference between randomly split groups points to their treatment.
- Genes set the range of possible traits, and different genotypes can respond differently to the same environment.
On the exam: When clones or randomly split groups differ, check their environments before blaming alleles.