Chiasma Studies in Structural Hybrids

VI. Heteromorphic bivalent and reciprocal translocation in Allium fistulosum

Abstract

Two heterozygotes were found in A. fistulosum (2n=16), one for a deficient satellite and one for a reciprocal translocation.
1. In the unequal arm of the deficiency heterozygote a single chiasma but not more than one was formed at MI in 80.4 percent of the cases; the frequency of equational AI separation attained to 79.5 percent.
2. In the translocation heterozygote, two pairs of chromosomes were distinguished, each being heteromorphic as to the lengths of the long arms. Frequencies of a single chiasma, but not more than one, formed in the long arms of the two pairs were 77.9 and 48.3 percent of the cases, respectively. In good conformity with these values, the frequencies of equational AI separation of the two pairs were 74.6 and 46.3 percent respectively.
3. These two findings are in very good agreement with the chiasmatype hypothesis accounting for the cytological configuration of the chiasmata.