BIOL1130 Lecture Notes - Lecture 11: Genetic Drift, Albinism, Conservation Genetics
Genes in Populations
What is evolution?
• Change in the genetic composition of a population (gene pool) across
generations
• Genetic variation is the basis of all evolution
• Two types:
o Microevolution – genetic change in gene pools
o Macroevolution – change above the species’ level (1→species)
Darwinian theory
• Two distinct components
o Evolution: descent with modification
o Natural selection: Darwin’s mechanism for evolutionary change
• Not the same thing…
o Evolution can occur by other ways
o Natural selection does not always lead to evolution
Natural Selection
• Variation exists between individuals of a population
• Many traits are inherited, many traits have a genetic basis
• Differential survival and reproductive success among individuals
• Outcome:
o Those alleles associated with greater survival or reproductive
success will increase in frequency the next generation
Are populations genetically variable?
• Tests for the existence of genetic variation
o Artificial selection – the power of artificial selection in causing
phenotypic change is well known to animal and plant breeders
o Molecular variation – protein electrophoresis (allozymes) known
as protein variation, the variations found in proteins called
allozymes
Thinking about populations in genetic terms
• Mendelian genetics – predicts proportions of different genotypes from
particular matings
o Doesn’t work for all populations – different types of matings all at
once
o
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o Assume there is random mating involved
o Expect to see 3 different genotypes
o If the species has genotypes in these proportions we say it is in the
Hardy-Weinberg Equilibrium
Assumptions of Hardy-Weinberg Equilibrium
• Random mating
• No mutation
• No migration
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