Genetic Variation and Change

• genetic variation: naturally occurring genetic differences among individuals of the same species
• crossing over: exchange of genetic material between adjacent chromatids of homologous chromosomes
• incomplete dominance: when the phenotype of a heterozygous resembles a blend of the two phenotypes
• co-dominance: when two alleles are equally dominant and equally recessive
• natural selection: the gradual process by which heritable traits become more common within a population due to environmental pressures
• founder’s effect: when a few individuals from a population start a new population with a different allele frequency than the original population.
• multiple alleles: having more than two alleles for a gene
• lethal alleles: alleles that are harmful to the organism and often cause death to the organism
• linkage: the tendency for two or more genes to be located on the same chromosome
• genetic drift: random change in allele frequency in a population due to chance
• founder effect: the process by which a small number of individuals start a new population and the new population is genetically different from the original population
• bottleneck effect: when a small population is exposed to a catastrophic event, the population is reduced to a small number of individuals