Lecture 7: Introduction to Population Genetics Flashcards
a locus (loci) is a
physical position of a gene or marker along a chromosome.
Alleles are..
The different forms of a gene
In a diploid organism the two alleles make up the…
genotype
An individual with two identical alleles (WW / ww)
Homozygote
An individual with two different alleles (Ww)
Heterozygote
A gene or phenotype with more than one form is
polymorphism
population genetics studies…
the frequencies of alleles in a population
Population genetics is studied in order to understand..
- The forces that determine the genetic composition a population, e.g. natural selection, mating system, migration, mutation, random genetic drift.
- The genetic basis, historian background and carrier frequencies of genetic diseases
p + q always =
when there are only two alleles
1
In a random-mating population the genotype frequencies are given by the ratio (&equation)
p^2:2pq:q^2
P^2 + 2pq + q^2 = 1
Assumptions of Hardy-Weinberg Eq
- Random Mating
- No natural selection
- a large population size
- no migration
- no mutation
Why is HWE useful?
- we can use allele rather than genotype frequencies to study population genetics (fewer alleles than genotypes, making calcs easier)
- It provided a description of how genetic variation is maintained
- Departures form HWE mean that some assumptions are not met
- It is useful in medical genetics (carrier freq)
Whats used to test HWE
CHI SQUARED
Chi squared equation
X^2 = sum of(O-E)^2/E
Degrees of freedom =
no. genotypes - no. parameters estimated - 1
