1. Chapter 17: Evolution of Populations
Section 17-1: Genes and Variation

2. Genetics Joins Evolutionary Theory
Heritable traits controlled by genes
Changes in genes/chromosomes result in variation
Genotype = particular allele combination, along with environmental condition determines phenotype
Natural selection acts on phenotype – some variations provide advantages, increasing fitness

3. Populations and Gene Pools
A gene pool consists of all the genes, including all the different alleles, for each gene present in a population
Study relative frequencies of alleles
Evolution is any change in the relative frequency of alleles in the gene pool of a population over time
Natural selection acts on individuals, but populations evolve

5. Sources of Genetic Variation
There are 3:
Mutations
Genetic recombination
Lateral gene transfer

6. Mutations
Mutations resulting in changes to phenotype may increase fitness, decrease fitness, or have no affect
Only matter in evolution if they are passed on – must occur in egg or sperm

7. Genetic Recombination
Occurs during sexual reproduction
Independent assortment produces millions of combinations
Crossing over

8. Lateral Gene Transfer
Organisms pass genes from one individual to another – not offspring
Can occur between organisms of same or different species
Variation increases in species that picks up “new” genes

9. Single-Gene Traits A trait controlled by only one gene
Can have 2 or 3 distinct phenotypes
Most common form of the allele can be dominant or recessive
Just because an allele is dominant does not mean it necessarily appears in greater frequency

11. Polygenic Traits Traits controlled by 2 or more genes
Each gene often has 2 or more alleles
Many possible genotypes/phenotypes