CHROMOSOME BEHAVIOUR IN ALOINEAE .1. NATURE AND SIGNIFICANCE OF E-TYPE BRIDGES

An E-type bridge is formed at AI of meiosis by a proximal connection between the long arm of an acrooentric chromosome and the short arm of its homologue. A long acentric fragment is also produced, consisting of an erstwhile long and short arm. Heteromorphy of homologues indicates that the bridge is formed as a result of crossing over in a non-inverted segment of chromosome translocated from one arm to the other by successive paracentric and pericentric inversions. There is no evidence that translocated centromere regions pair. E-type bridges occur in the Aloineae (Liliaceae) in 20 out of 163 taxa studied. It is suggested that a high incidence of E-type bridges is indicative of inter-specific hybridity. © 1969 Springer-Verlag.