Population Genetics II Flashcards
What does population genetics help us to understand?
How selection, drift and migration acts on variation
Example of pre existing variation then environmental change and results in selection of new allele
Fortis
Magnirostris (big beak)
Drought generated strong competition between the two. Strong competition for intermediate sized seeds.
Drove selection for small beak
Pre existing genetic variation, environmental changes, rapid evolutionary response
Graph
XXX?
A genome size increases, mutation rate per nucleotide per replication decreases
Most mutations are
Deleterious (reduce fitness)
X
Genetically engineered 50 random mutations into virus
About 40% mutations were lethal
- Mutation introduced
2. Selection selects against
- A mutation introduces a new deleterious variant into the population
- Selection reduces the frequency of this mutation (this low fitness allele)
What allele leads to CF
Homozygous
What’s in the lungs of people with CF
Long term bacterial colonisation
If natural selection removes deleterious mutations, why can we find alleles that are deleterious at a high frequency? (Eg. We find the homozygous deleterious cystic fibrosis allele)
Deleterious recessive mutations are hidden from selection by heterozygosity
Spontaneous mutation continually decreases low fitness alleles
What does
Spontaneous mutation continually decreases low fitness alleles
Mean
NS selects and removes deleterious mutations but natural spontaneous mutation simply replenishes them
Sticklebacks are
An example of selection on standing variation
Where did the low body armour allele come from?
X
Why are bacteria good to do experiments on?
Can cryogenically freeze them Genomes cheap to sequence Short generation time Small Fitness can be measured
