Non-random patterns of non-disjunctional orientation in trivalents of multiple Robertsonian heterozygotes of Dichroplus pratensis (Acrididae)
Metaphase I orientation of centric fusion trivalents was studied in 24 single, 19 double and 3 triple heterozygotes of Dichroplus pratensis. Different populations of this South American melanopline grasshopper are polymorphic for seven Robertsonian fusions, and the polymorphisms seem to be stable. S...
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| Autores principales: | , |
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1994
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| Acceso en línea: | https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00166707_v92_n3_p155_Mirol http://hdl.handle.net/20.500.12110/paper_00166707_v92_n3_p155_Mirol |
| Aporte de: |
| Sumario: | Metaphase I orientation of centric fusion trivalents was studied in 24 single, 19 double and 3 triple heterozygotes of Dichroplus pratensis. Different populations of this South American melanopline grasshopper are polymorphic for seven Robertsonian fusions, and the polymorphisms seem to be stable. Several cytogenetic factors involved in the orientation and segregation of the meiotic configurations such as chromosomal length, symmetry and number and position of chiasmata, have been analysed in previous works. In this paper we study another factor that is relevant in the above respect in individuals with more than one heterozygous fusion: interaction among configurations regarding orientation. Our results indicate that, when there are two or three trivalents present in the MI cell, there is an interaction in such a way that the number of metaphases in which the two or three trivalents are non-disjunctionally oriented is always significantly higher than expected under a hypothesis of independence. However, the number of cells in which all trivalents are disjunctionally oriented does not decrease significantly, so an increase of unbalanced gametes due to this factor is not expected. The stability of the polymorphisms would thus not be affected. © 1994 Kluwer Academic Publishers. |
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