Forces that hold variation in balance

Science · Genetics & Evolution · ages 18-20

Name ______________________ Date ____________

Which force alone creates brand new alleles?
- Drift
- Migration
- Mutation
When do allele frequencies freeze under Hardy Weinberg?
- When migrants arrive daily
- When no force acts at all
- When mutation runs fast
p squared plus 2pq plus q squared describes the no force baseline.
Circle one: True False
One migrant per generation joins a neighbour group. What follows over time?
- Both groups lose all variation
- Mutation stops entirely
- The groups blend toward matching frequencies
Why does a harmful recessive linger instead of vanishing?
- It hides in healthy heterozygotes
- It helps carriers survive
- Selection favours rare traits
4 in 100 people show a recessive trait. Type q, the recessive allele frequency.
Answer: ______________
A harmful allele stays common despite selection. Which balance could explain it?
- Steady newcomers ferry it in each generation
- The square root rule broke down
- Homozygotes stopped breeding
Which ranking of speed is right?
- Mutation beats migration short term
- Migration beats mutation short term
- Drift beats both always

Answer key

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

Mutation · Mutation is the only supply of novelty; the rest move variation around.
When no force acts at all · The stillness needs no mutation, selection, drift, flow, or nonrandom mating.
True · That sum is the steady state every force disturbs.
The groups blend toward matching frequencies · Steady migration pulls frequencies together a little each generation.
It hides in healthy heterozygotes · Most copies sit beyond selection's reach in carriers.
0.2 · q is the square root of 0.04, which is 0.2.
Steady newcomers ferry it in each generation · Inputs like migration can balance removal by selection.
Migration beats mutation short term · Migration moves whole allele sets fast; mutation trickles.