Indexed on: 01 Oct '01Published on: 01 Oct '01Published in: Russian Journal of Genetics
Using computer simulation, selection response of three genome patterns—polygenes, mobile genetic elements (MGEs), and labels of identity by origin (LIOs)—were studied. In each generation of selection, variability of each pattern type was described by an UPGMA tree. Stringent positive truncation (+) selection on an additive polygenic trait and recombination between segments of the genetic map were considered. MGEs were classified into three groups: modifiers (enhancers) of the polygenic expression, markers, and independent copies. It was shown that at generations 30 to 40, 95–96% and 70–80% of respectively enforced and non-enforced active polygenic alleles were fixed (2–3% and 16–17% lost). In all generations, Hnk≤ max Dnkof the length of the maximal route along the tree. At the same time, modifier MGEs were fixed for 85–88% (lost for 11–12%); marker MGEs, for 60–70% (lost for 21–25%); and independent copies, for 30–40 (lost for 50–60%). The behavior of independent MGE copies was generally consistent with the predictions of the genetic drift theory, modifier MGEs behaved similarly to the modified polygenes, and marker MGEs exhibited intermediate properties. The LIO patterns showed rapid homozygotization: their variability dropped dramatically between generations 10 and 30. In F50, the final consensus pattern of polygenes included 16 out of 18 enforced and 18 out of 21 non-enforced polygenic alleles. The fixation/loss ratios were 16 : 3 for modifier MGEs, 15 : 6 for marker MGEs, and 25 : 28 (with 7 polymorphic) for independent copies. The LIO consensus pattern contained 13 out of 100 original markers, which formed 26 fragments of one to ten map segments in size; 21 fragments contained active polygenic alleles, and 14 of them had also modifier MGEs. Recombinational shuffling of patterns was not completed. In the course of selection, active polygenic alleles take along adjacent segments, including those containing modifier MGEs and markers. These constitute the conservative part of all consensus patterns while the remaining segments are random.