Effects of centric fusions on chiasma frequency and position in Leptysma argentina (Acrididae: Orthoptera) I. Spontaneous and stable polymorphic centric fusions

Leptysma argentina is a highly polymorphic South-American grasshopper from the cytological point of view; all populations so far studied carry a polymorphic fusion between pairs 3 and 6. In heterozygotes, the trivalent 3-3/6-6 shows alternate orientation in 97.17% of the cells. Trivalent chiasma fre...

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Autor principal: Colombo, Pablo Cesar
Publicado: 1987
Acceso en línea:https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00166707_v72_n3_p171_Colombo
http://hdl.handle.net/20.500.12110/paper_00166707_v72_n3_p171_Colombo
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Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires
id paper:paper_00166707_v72_n3_p171_Colombo
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spelling paper:paper_00166707_v72_n3_p171_Colombo2023-06-08T14:38:35Z Effects of centric fusions on chiasma frequency and position in Leptysma argentina (Acrididae: Orthoptera) I. Spontaneous and stable polymorphic centric fusions Colombo, Pablo Cesar Leptysma argentina is a highly polymorphic South-American grasshopper from the cytological point of view; all populations so far studied carry a polymorphic fusion between pairs 3 and 6. In heterozygotes, the trivalent 3-3/6-6 shows alternate orientation in 97.17% of the cells. Trivalent chiasma frequency is significantly lower than in the combined 3 and 6 bivalents of the standard homozygote; besides, there is a marked displacement of chiasmata to a distal position. In structural homozygotes the same effects, but not so marked, were observed. One individual was a double heterozygote for both the polymorphic centric fusion and a spontaneous one between pairs 5 and 7. The presence of a fragment, sometimes associated with the centromeric region of the nonfused 5 chromosome, was detected in more than 50% of the cells. The orientation of trivalent 5-5/7-7 in metaphase I was highly irregular (36% linear orientation). Neither frequency nor position of chiasmata were altered in trivalent 5-5/7-7 when compared with bivalents 5+7 of normal individuals. The results suggest that proximal and interstitial chiasma reduction observed in trivalent 3-3/6-6 of L. argentina is due to a later adaptation to the polymorphic condition or a fortuitous genetic condition present in the original mutant, rather than to a direct effect of the fusion itself on chiasma distribution. © 1987 Dr W. Junk Publishers. Fil:Colombo, P.C. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. 1987 https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00166707_v72_n3_p171_Colombo http://hdl.handle.net/20.500.12110/paper_00166707_v72_n3_p171_Colombo
institution Universidad de Buenos Aires
institution_str I-28
repository_str R-134
collection Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
description Leptysma argentina is a highly polymorphic South-American grasshopper from the cytological point of view; all populations so far studied carry a polymorphic fusion between pairs 3 and 6. In heterozygotes, the trivalent 3-3/6-6 shows alternate orientation in 97.17% of the cells. Trivalent chiasma frequency is significantly lower than in the combined 3 and 6 bivalents of the standard homozygote; besides, there is a marked displacement of chiasmata to a distal position. In structural homozygotes the same effects, but not so marked, were observed. One individual was a double heterozygote for both the polymorphic centric fusion and a spontaneous one between pairs 5 and 7. The presence of a fragment, sometimes associated with the centromeric region of the nonfused 5 chromosome, was detected in more than 50% of the cells. The orientation of trivalent 5-5/7-7 in metaphase I was highly irregular (36% linear orientation). Neither frequency nor position of chiasmata were altered in trivalent 5-5/7-7 when compared with bivalents 5+7 of normal individuals. The results suggest that proximal and interstitial chiasma reduction observed in trivalent 3-3/6-6 of L. argentina is due to a later adaptation to the polymorphic condition or a fortuitous genetic condition present in the original mutant, rather than to a direct effect of the fusion itself on chiasma distribution. © 1987 Dr W. Junk Publishers.
author Colombo, Pablo Cesar
spellingShingle Colombo, Pablo Cesar
Effects of centric fusions on chiasma frequency and position in Leptysma argentina (Acrididae: Orthoptera) I. Spontaneous and stable polymorphic centric fusions
author_facet Colombo, Pablo Cesar
author_sort Colombo, Pablo Cesar
title Effects of centric fusions on chiasma frequency and position in Leptysma argentina (Acrididae: Orthoptera) I. Spontaneous and stable polymorphic centric fusions
title_short Effects of centric fusions on chiasma frequency and position in Leptysma argentina (Acrididae: Orthoptera) I. Spontaneous and stable polymorphic centric fusions
title_full Effects of centric fusions on chiasma frequency and position in Leptysma argentina (Acrididae: Orthoptera) I. Spontaneous and stable polymorphic centric fusions
title_fullStr Effects of centric fusions on chiasma frequency and position in Leptysma argentina (Acrididae: Orthoptera) I. Spontaneous and stable polymorphic centric fusions
title_full_unstemmed Effects of centric fusions on chiasma frequency and position in Leptysma argentina (Acrididae: Orthoptera) I. Spontaneous and stable polymorphic centric fusions
title_sort effects of centric fusions on chiasma frequency and position in leptysma argentina (acrididae: orthoptera) i. spontaneous and stable polymorphic centric fusions
publishDate 1987
url https://bibliotecadigital.exactas.uba.ar/collection/paper/document/paper_00166707_v72_n3_p171_Colombo
http://hdl.handle.net/20.500.12110/paper_00166707_v72_n3_p171_Colombo
work_keys_str_mv AT colombopablocesar effectsofcentricfusionsonchiasmafrequencyandpositioninleptysmaargentinaacrididaeorthopteraispontaneousandstablepolymorphiccentricfusions
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