Transcript Evolution of Populations

Evolution of Populations
Gene Pool
• All of the genes
(including all of the
alleles of those
genes) that are in a
population
Relative Frequency
• The number of times an allele occurs
Evolution
• (In genetics), evolution is anytime there is a
change in the frequency in alleles in a
population.
Variation
• Mutations = Mistakes
or damage to DNA
Sometimes effect
phenotype but not
always
• Gene Shuffling= 23
pairs of chromosomes
can produce 8.4
million combinations
of genes
Single / Polygenic
• Single Gene Traits
• A single gene has two
alleles
• Usually a dominant
and recessive
• Only two distinct
phenotypes can be
shown
• Polygenic Traits
• Often has two or
more genes
• Each gene has two or
more alleles
• Many possible
genotypes and
phenotypes
Natural Selection on polygenic traits can affect the
distribution of traits in three ways
• Directional
Selection
• Stabilizing
Selection
• Disruptive
Selection
Directional Selection
Disruptive Selection
Stabilizing Selection
Genetic Drift: in small populations an individual that carries a particular
allele may leave more offspring than others and over time that trait may
become more prevalent in the population
Founder Effect
• The new allele frequency is different from the
original population
Hardy Weinberg
• Hardy Weinberg
Principle states that the
allele frequency in a
population will remain
at genetic equilibrium
unless one or more
factors cause it to
change. If they do not
change, the population
will not evolve.
Genetic Equilibrium
• When allele
frequencies
in a
population
remain
constant,
Hardy Weinberg Principle – Five Conditions
• 1. Random Mating
• 2. Large population
• 3. No Immigration or
Emigration
• 4. No Mutations
• 5. No Natural Selection