Organization of Retrotransposons and Microsatellites in Cereal GenomesA HSchulmanauthorP KGuptaauthorR KVarshneyauthorOur understanding of genome organization has its roots in postwar interest in the effects of radiation. Observations on the relationship between doses of ionizing radiation and the frequency of mutations (Abrahamson et ai., 1 973; Trujillo and Dugan, 1 975) indicated that the size of the genetic target receiving the radiation dose varied considerably between organisms. By the beginning of the 1 970s, this phenomenon had come to be known as the "Cvalue paradox" (Thomas, 1 97 1 ). The paradox was that the total genome size, or C-value, varied widely within a given clade of organisms and bore no relationship to organismal complexity. For example, two legumes within the same genus, Vida/aba and Vida sativa, have haploid genomes of 1 3. 1 x 1 09 and 2.2 x109 respectively, but differ very little morphologically. This observation has been fully confIrmed by the large-scale determination of genome sizes of many plants (http://www. rbgkew.org.uk/cvalues), within which genome size varies from about 107 bp in Cardamine and Arabidopsis among the Crucifereae to nearly 1 011 bp in Fritillaria among the Lilliaceae. Within the cereals, rice (Oryza sativa) has a compact genome of 4.8 x 1 08 bp, ranging upwards through sorghum (7.35 x 1 08), maize (26.7 x 1 08), and barley (54.4 x 1 08 bp)......Genetics and GenomicsAgriculture-Farming, Production, Technology, Economics2005Springer NetherlandsBook Section