Puzzling Chromosome Behavior in Triploid Females of Drosophila melanogaster |
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Authors: | Chubykin V. L. |
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Affiliation: | (1) Vavilov Institute of General Genetics, Russian Academy of Sciences, ul. Gubkina 3, Moscow, 119991, Russia |
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Abstract: | Based on a particular formation of the chromocenter and trivalents in triploid Drosophila females, as well as on asynapsis in pericentromeric regions (which is a result of trivalent competition), an explanation for the increased frequency of crossing over and nonrandom segregation of the X chromosomes and autosomes in the first meiotic division is suggested. It is proposed that a delay in pairing of the pericentromeric heterochromatic chromosome regions combined into a single chromocenter leads to the following: (1) formation of the heteroduplex structures (X structures) takes more time and, consequently, their number and the frequency of crossing over in the paired chromosome regions increases; (2) in nonhomologous chromosomes, the chromocentral connections, which normally degrade in prometaphase, are retained to fulfill a function of coorientation during the first meiotic division. |
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