Flashcards in Population Genetics Deck (12):
List the factors that can alter the Hardy-Weinberg equilibrium
1. Genetic drift and bottlenecks
3. Positive assortment mating
4. Negative assortment mating
6. Natural selection
How do you calculate sampling variance?
What is genetic drift?
Variation in allele frequencies due to chance disappearance of particular alleles
More of an effect in small populations
What is a population bottleneck?
Sharp reduction in population due to environmental events
Give an example of a population bottleneck
Cheetahs experienced a population bottleneck around 10,000 years ago.
As a result have very low levels of genetic variation
European bison- went through bottleneck in early 20th century. All today are descendants of 12 individuals, and have subsequently very low genetic diversity
(Luenser et al., 2005)
Give examples of genetic drift
• Maintain 2 populations of red and white eyed drosophila in a cage and measure phenotype frequency. Eventually one colour goes extinct
In small populations more likely:
Isolated populations like Finland
• Set of 33 damaging recessive alleles found nowhere else in the world (inbreeding)
Define inbreeding depression
Reduced biological fitness as a result of inbreeding
Give an example of migration affecting HW
Admixture between human populations of African and European origin
Admixture between Cuban brown anole and native lizards when introduced into areas such as Florida- freely interbred
Give examples of positive assortment mating
Humans- dependant on factors such as race, religion, education, collar size
Animals- mating more likely between individuals of similar size and colour.
Give examples of negative assortment mating
Plants- self-incompatibility alleles act as outbreeding mechanism
Wolves in Yellowstone- grey with black
(Hendrick et al., 2016)
BRUCE effect in mice- terminate pregnancy when exposed to scent of unfamiliar male
Humans- Tay Sachs in Ashkenazi Jews, testing people for heterozygosity and match-making
Explain how mutation affects HW and give examples
Allele frequencies will change if new alleles emerge in a population
Cytochrome C mutations often have no effect on fitness so accumulate in populations. Allele frequencies therefore give information on when species diverged from each other