Schematic representation of genomic mosaicism as a result of ancestral admixture. An admixed individual derived from two founders in several generations of recombination. The chromosomes of the two founders (shown in different colors) are combined by several generations of random mating to produce present day admixed individual. A DNA sequence of any admixed individual is a mosaic of its founders’ DNA segments. A classic example in humans is the African-American population. The two ancestral populations, European and African ancestry, are represented by dark blue and red chromosomes, respectively. Individuals in the subsequent generation may or may not receive an intact chromosome of their ancestor. As generations continue, mosaics develop for chromosomes 1 and 2 as a result of recombination during meiosis. Chromosomal block sizes are expected to decay with the number of generations of admixture. Only those meiotic crossovers that occur at loci where the paired homologous chromosomes have different ancestries will cause ancestry blocks to decay in size and can be detected using ancestry informative markers (AIMs).