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Chiasma Studies in Structural Hybrids

1960; International Society of Cytology; Volume: 25; Issue: 3-4 Linguagem: Inglês

10.1508/cytologia.25.468

1348-7019

Hiroshi Kayano,

Plant Virus Research Studies

1. In reciprocal translocation heterozygotes of Disporum sessile, both ends of the two pairing chromosomes were distinguished. Relationship was found between chiasma formation and crossing-over by AII crossover chromatid analysis.2. Since no, one, two, and three chiasmata were observed at MI in the pairing segments with respective frequencies 48.8, 34.6, 14.8, and 1.8 per cent of PMCs, the following values were calculated on the basis of the chiasmatype hypothesis: 43.4 per cent for the frequency of equational separation of the distal heteromorphic ends, and 25.6 per cent for the frequency of crossover chromatids. Actually, 41.6 per cent of the half-tetrads revealed equational AI separation of the heteromorphic ends, and 25.1 per cent of the chromatids were crossovers. Therefore, it is very likely that the chiasmata in the pairing segments of the present heteromorphic chromosomes are closely related to crossing-over.