Download Chapter 17.1-Genes and Variation

Chapter 17:
Evolution of Populations
Chapter 17.1 (Pgs 482-486):
Genes and Variation
Phenotypic Variation
- Most organisms contain two sets of genes
- One allele from each parent
- Different combinations of alleles and
environment produce variation in phenotypes
- Natural selection acts directly on phenotypes,
not the alleles
Populations and Gene Pools
- A group of individuals of the same
species that mate and produce
offspring is called a population
- These individuals share a gene pool,
all the genes and alleles for each
gene in a population
Allele Frequency
- The # of times an allele occurs in
a gene pool, compared to the
total # of alleles for that gene
- Evolution occurs when allele
frequency in a population
changes over time
- Populations, not individuals, evolve
Single-Gene Traits
- Are controlled by only one gene
- Only have two alleles
- May only have two or three distinct
phenotypes
Polygenic Traits
- Are controlled by two or more genes
- Each gene has two or more alleles
- Has many possible genotypes and even
more different phenotypes