A1 Refereed original research article in a scientific journal
Interaction of B chromosomes with A or B chromosomes in segregation in insects
Authors: Nokkala S, Nokkala C
Publisher: KARGER
Publication year: 2004
Journal:: Cytogenetic and Genome Research
Journal name in source: CYTOGENETIC AND GENOME RESEARCH
Journal acronym: CYTOGENET GENOME RES
Volume: 106
Issue: 2-4
First page : 394
Last page: 397
Number of pages: 4
ISSN: 1424-8581
DOI: https://doi.org/10.1159/000079317
Abstract
Additional or B chromosomes not belonging to the regular karyotype of a species are found in many animal and plant groups. They form a highly heterogeneous group with respect to their morphology and behaviour both in mitosis and meiosis. Achiasmatic mechanisms that ensure the segregation of a B chromosome from another B chromosome or from an A chromosome are reviewed. An achiasmatic mechanism characterized by the "distance pairing" of segregating univalents at metaphase I was found to be responsible for the preferential segregation of B chromosome univalents in Hemerobius marginatus L. ( Neuroptera), and a mechanism characterized by the "touch and go pairing" of segregating univalents was responsible for the highly regular segregation of a B chromosome and the X chromosome in Rhinocola aceris ( L.) ( Psylloidea, Homoptera). The latter mechanism resulted in the integration of a B chromosome to the A chromosome set as a Y chromosome in a psyllid species Cacopsylla peregrina (Frst.). Furthermore, B chromosomes can disturb the regular segregation of the achiasmatic X and Y chromosomes resulting in the formation of X0/ XY polymorphism in a population, which might precede the loss of the Y chromosome. The absence of observations on accurately functioning achiasmatic segregation mechanisms in grasshoppers ( Orthoptera) was attributed to the X and B chromosomes, which re-orient one or several times during metaphase I. Apparently, these re-orientations mask any achiasmatic segregation mechanism that might operate during meiotic prophase in these insects. Copyright (C) 2004 S. Karger AG, Basel.
Additional or B chromosomes not belonging to the regular karyotype of a species are found in many animal and plant groups. They form a highly heterogeneous group with respect to their morphology and behaviour both in mitosis and meiosis. Achiasmatic mechanisms that ensure the segregation of a B chromosome from another B chromosome or from an A chromosome are reviewed. An achiasmatic mechanism characterized by the "distance pairing" of segregating univalents at metaphase I was found to be responsible for the preferential segregation of B chromosome univalents in Hemerobius marginatus L. ( Neuroptera), and a mechanism characterized by the "touch and go pairing" of segregating univalents was responsible for the highly regular segregation of a B chromosome and the X chromosome in Rhinocola aceris ( L.) ( Psylloidea, Homoptera). The latter mechanism resulted in the integration of a B chromosome to the A chromosome set as a Y chromosome in a psyllid species Cacopsylla peregrina (Frst.). Furthermore, B chromosomes can disturb the regular segregation of the achiasmatic X and Y chromosomes resulting in the formation of X0/ XY polymorphism in a population, which might precede the loss of the Y chromosome. The absence of observations on accurately functioning achiasmatic segregation mechanisms in grasshoppers ( Orthoptera) was attributed to the X and B chromosomes, which re-orient one or several times during metaphase I. Apparently, these re-orientations mask any achiasmatic segregation mechanism that might operate during meiotic prophase in these insects. Copyright (C) 2004 S. Karger AG, Basel.
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