Transcript Allele frequencies

I. Allele frequencies and gene pool
A. Gene Pool:
Total genetic information available in population
B. Allele frequency is determined by dividing number of
certain allele by total number of alleles.
1.
P+Q=1
1. P = number of recessive/total number of alleles
2. Q =number of dominant/total number of alleles
C. Use allele frequency to Predict Phenotypes
P2 + 2PQ + Q2 = 1
II. Hardy Weinberg Equilibrium
A. Allele frequencies in a population remain the
same from generation to generation unless acted
on by outside influences.
B. Assumptions about an ideal “made up”
population that is not evolving
1. No net mutations occur; allele frequencies do not
change because of mutation.
2. Individuals neither enter nor leave the population.
3. The population is large
4. Individuals mate randomly.
5. Natural Selection does not occur.
III. Disruption of Genetic Equilibrium
A. Mutation
1. can produce totally new alleles for a trait
2. most harmful
3. beneficial are important for evolution
B. Migration (Gene Flow)
1. Immigration
a) Movement of individuals into a population
2. Emigration
a) movement of individuals out a population
b) Gene flow
(1) Process of genes moving from one population to another
C. Genetic Drift
1. Allele frequencies change as a result of random
events or chance
2. Small populations
a) Founders effect
b) Bottle neck
D. NonRandom Mating
1. Many species do not mate randomly
2. based on
a) geographic proximity
b) similar physical characteristic
(1) assortative mating
E. Natural Selection
1. Stabilizing selection
a) Individuals with average form of trait have highest
fitness
b) Extreme forms have lower fitness
(1) Large – seen
(2) Small – not fast
2. Directional selection
a) One extreme form has greater fitness then average
b) Anteaters longer tongue more effective
3. Disruptive Selection
a) Either extreme have greater fitness
F. Sexual Selection
1. Colors
2. Females choose males based on certain traits
3. Extreme traits give female indication of quality
of males genes
Summary
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Causes of variation
predicting phenotype
Hardy Weinberg equilibrium
6 things which disrupt genetic equilibrium