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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todo:paper_00166707_v72_n3_p171_Colombo2023-10-03T14:14:23Z Effects of centric fusions on chiasma frequency and position in Leptysma argentina (Acrididae: Orthoptera) I. Spontaneous and stable polymorphic centric fusions Colombo, P.C. 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. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_00166707_v72_n3_p171_Colombo |
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Universidad de Buenos Aires |
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I-28 |
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R-134 |
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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. |
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JOUR |
| author |
Colombo, P.C. |
| spellingShingle |
Colombo, P.C. Effects of centric fusions on chiasma frequency and position in Leptysma argentina (Acrididae: Orthoptera) I. Spontaneous and stable polymorphic centric fusions |
| author_facet |
Colombo, P.C. |
| author_sort |
Colombo, P.C. |
| 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 |
| url |
http://hdl.handle.net/20.500.12110/paper_00166707_v72_n3_p171_Colombo |
| work_keys_str_mv |
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