Synapsis in Robertsonian heterozygotes and homozygotes of Dichroplus pratensis (Melanoplinae, Acrididae) and its relationship with chiasma patterns
Dichroplus pratensis has a complex system of Robertsonian rearrangements with central-marginal distribution; marginal populations are standard telocentric. Standard bivalents show a proximal-distal chiasma pattern in both sexes. In Robertsonian individuals a redistribution of chiasmata occurs: proxi...
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2001
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| Acceso en línea: | https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00180661_v134_n3_p245_Marti http://hdl.handle.net/20.500.12110/paper_00180661_v134_n3_p245_Marti |
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paper:paper_00180661_v134_n3_p245_Marti2023-06-08T14:39:16Z Synapsis in Robertsonian heterozygotes and homozygotes of Dichroplus pratensis (Melanoplinae, Acrididae) and its relationship with chiasma patterns Bidau, Claudio Juan animal experiment animal tissue article chromosomal localization chromosome arm chromosome bivalent chromosome chiasm chromosome pairing gene fusion grasshopper heterozygote homozygote karyotype male metaphase nonhuman pachytene prophase Robertsonian chromosome translocation transmission electron microscopy Animals Chromosome Pairing Chromosomes Crossing Over, Genetic Grasshoppers Heterozygote Homozygote Karyotyping Male Meiosis Metaphase Testis Acrididae Animalia Dichroplus Invertebrata Melanoplinae Robertsonia Dichroplus pratensis has a complex system of Robertsonian rearrangements with central-marginal distribution; marginal populations are standard telocentric. Standard bivalents show a proximal-distal chiasma pattern in both sexes. In Robertsonian individuals a redistribution of chiasmata occurs: proximal chiasmata are suppressed in fusion trivalents and bivalents which usually display a single distal chiasma per chromosome arm. In this paper we studied the synaptic patterns of homologous chromosomes at prophase I of different Robertsonian status in order to find a mechanistic explanation for the observed phenomenon of redistribution of chiasmata. Synaptonemal complexes of males with different karyotypes were analysed by transmission electron microscopy in surface-spread preparations. The study of zygotene and early pachytene nuclei revealed that in the former, pericentromeric regions are the last to synapse in Robertsonian trivalents and bivalents and normally remain asynaptic at pachytene in the case of trivalents, but complete pairing in bivalents. Telocentric (standard) bivalents usually show complete synapsis at pachytene, but different degrees of interstitial asynapsis during zygotene, suggesting that synapsis starts in opposite (centromeric and distal) ends. The sequential nature of synapsis in the three types of configuration is directly related to their patterns of chiasma localisation at diplotene-metaphase I, and strongly supports our previous idea that Rb fusions instantly produce a redistribution of chiasmata towards chromosome ends by reducing the early pairing regions (which pair first, remain paired longer and thus would have a higher probability of forming chiasmata) from four to two (independently of the heterozygous or homozygous status of the fusion). Pericentrometric regions would pair the last, thus chiasma formation is strongly reduced in these areas contrary to what occurs in telocentric bivalents. Fil:Bidau, C.J. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. 2001 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00180661_v134_n3_p245_Marti http://hdl.handle.net/20.500.12110/paper_00180661_v134_n3_p245_Marti |
| institution |
Universidad de Buenos Aires |
| institution_str |
I-28 |
| repository_str |
R-134 |
| collection |
Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) |
| topic |
animal experiment animal tissue article chromosomal localization chromosome arm chromosome bivalent chromosome chiasm chromosome pairing gene fusion grasshopper heterozygote homozygote karyotype male metaphase nonhuman pachytene prophase Robertsonian chromosome translocation transmission electron microscopy Animals Chromosome Pairing Chromosomes Crossing Over, Genetic Grasshoppers Heterozygote Homozygote Karyotyping Male Meiosis Metaphase Testis Acrididae Animalia Dichroplus Invertebrata Melanoplinae Robertsonia |
| spellingShingle |
animal experiment animal tissue article chromosomal localization chromosome arm chromosome bivalent chromosome chiasm chromosome pairing gene fusion grasshopper heterozygote homozygote karyotype male metaphase nonhuman pachytene prophase Robertsonian chromosome translocation transmission electron microscopy Animals Chromosome Pairing Chromosomes Crossing Over, Genetic Grasshoppers Heterozygote Homozygote Karyotyping Male Meiosis Metaphase Testis Acrididae Animalia Dichroplus Invertebrata Melanoplinae Robertsonia Bidau, Claudio Juan Synapsis in Robertsonian heterozygotes and homozygotes of Dichroplus pratensis (Melanoplinae, Acrididae) and its relationship with chiasma patterns |
| topic_facet |
animal experiment animal tissue article chromosomal localization chromosome arm chromosome bivalent chromosome chiasm chromosome pairing gene fusion grasshopper heterozygote homozygote karyotype male metaphase nonhuman pachytene prophase Robertsonian chromosome translocation transmission electron microscopy Animals Chromosome Pairing Chromosomes Crossing Over, Genetic Grasshoppers Heterozygote Homozygote Karyotyping Male Meiosis Metaphase Testis Acrididae Animalia Dichroplus Invertebrata Melanoplinae Robertsonia |
| description |
Dichroplus pratensis has a complex system of Robertsonian rearrangements with central-marginal distribution; marginal populations are standard telocentric. Standard bivalents show a proximal-distal chiasma pattern in both sexes. In Robertsonian individuals a redistribution of chiasmata occurs: proximal chiasmata are suppressed in fusion trivalents and bivalents which usually display a single distal chiasma per chromosome arm. In this paper we studied the synaptic patterns of homologous chromosomes at prophase I of different Robertsonian status in order to find a mechanistic explanation for the observed phenomenon of redistribution of chiasmata. Synaptonemal complexes of males with different karyotypes were analysed by transmission electron microscopy in surface-spread preparations. The study of zygotene and early pachytene nuclei revealed that in the former, pericentromeric regions are the last to synapse in Robertsonian trivalents and bivalents and normally remain asynaptic at pachytene in the case of trivalents, but complete pairing in bivalents. Telocentric (standard) bivalents usually show complete synapsis at pachytene, but different degrees of interstitial asynapsis during zygotene, suggesting that synapsis starts in opposite (centromeric and distal) ends. The sequential nature of synapsis in the three types of configuration is directly related to their patterns of chiasma localisation at diplotene-metaphase I, and strongly supports our previous idea that Rb fusions instantly produce a redistribution of chiasmata towards chromosome ends by reducing the early pairing regions (which pair first, remain paired longer and thus would have a higher probability of forming chiasmata) from four to two (independently of the heterozygous or homozygous status of the fusion). Pericentrometric regions would pair the last, thus chiasma formation is strongly reduced in these areas contrary to what occurs in telocentric bivalents. |
| author |
Bidau, Claudio Juan |
| author_facet |
Bidau, Claudio Juan |
| author_sort |
Bidau, Claudio Juan |
| title |
Synapsis in Robertsonian heterozygotes and homozygotes of Dichroplus pratensis (Melanoplinae, Acrididae) and its relationship with chiasma patterns |
| title_short |
Synapsis in Robertsonian heterozygotes and homozygotes of Dichroplus pratensis (Melanoplinae, Acrididae) and its relationship with chiasma patterns |
| title_full |
Synapsis in Robertsonian heterozygotes and homozygotes of Dichroplus pratensis (Melanoplinae, Acrididae) and its relationship with chiasma patterns |
| title_fullStr |
Synapsis in Robertsonian heterozygotes and homozygotes of Dichroplus pratensis (Melanoplinae, Acrididae) and its relationship with chiasma patterns |
| title_full_unstemmed |
Synapsis in Robertsonian heterozygotes and homozygotes of Dichroplus pratensis (Melanoplinae, Acrididae) and its relationship with chiasma patterns |
| title_sort |
synapsis in robertsonian heterozygotes and homozygotes of dichroplus pratensis (melanoplinae, acrididae) and its relationship with chiasma patterns |
| publishDate |
2001 |
| url |
https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00180661_v134_n3_p245_Marti http://hdl.handle.net/20.500.12110/paper_00180661_v134_n3_p245_Marti |
| work_keys_str_mv |
AT bidauclaudiojuan synapsisinrobertsonianheterozygotesandhomozygotesofdichropluspratensismelanoplinaeacrididaeanditsrelationshipwithchiasmapatterns |
| _version_ |
1768544162853945344 |