Genetic Variation in Natural Populations

Abstract

Genetic variation among individuals within populations and among populations can be assessed at the chromosomal, protein, or DNA sequence level. The best tool or approach depends on the question being asked. Variation in the number or structure of chromosomes can result in reproductive incompatibilities and reduced fitness that influences the success of conservation efforts. Differences in amino acid sequence that alter the electrophoretic mobility of proteins, termed allozymes, were widely used to measure genetic variation and population differentiation on a gene-by-gene basis prior to advances in DNA sequencing. Mitochondria and chloroplasts contain circular DNA molecules that are usually inherited from one parent and are useful for assessing population history and structure. Most studies of genetic variation now rely on the analysis of single nucleotide polymorphisms (SNPs)—variations in nucleotides at a single location within the genome—to understand both selectively neutral and adaptive processes.