Why continuous traits need variance

Science · Genetics & Evolution · ages 18-20

Name ______________________ Date ____________

Continuous traits usually show a bell shaped curve across a population.
Circle one: True False
Total phenotypic variance splits into which two parts?
- Additive and lethal
- Parental and offspring
- Genetic and environmental
Which division gives broad sense heritability?
- Genetic over total
- Environmental over total
- Total over genetic
Surroundings become far more uniform while genes stay the same. What happens to heritability?
- It rises
- It falls
- It freezes at 0.5
Genetic variance is 48 and total variance is 120. Type the heritability.
Answer: ______________
Which part of genetic variance answers selection?
- The dominance part
- The additive part
- The interaction part
A report says a heritability of 0.6 proves most of your score comes from genes. What is wrong?
- It confuses population variation with one person
- It uses the wrong decimal places
- It ignores the bell curve shape
Two groups share the same alleles, but one is better fed and taller. What does this show?
- Genes play no role here
- Heritability must be zero
- Heritability is tied to one setting

Answer key

For grown-ups. Fold this page away before handing over the rest.

True · Many small genetic pushes plus setting effects pile into a bell shape.
Genetic and environmental · Total variance is genetic variance plus environmental variance.
Genetic over total · Heritability is genetic variance divided by total variance.
It rises · Less environmental variance means the genetic share grows.
0.4 · 48 divided by 120 is 0.4.
The additive part · Narrow sense heritability uses the additive part that responds to selection.
It confuses population variation with one person · Heritability splits variation in a group, never causes in one person.
Heritability is tied to one setting · The same genes give different looks when the setting changes.