Showing papers by "Nanyang Technological University published in 1967"

The Behaviour of Interchanges in Secale Hybrids

Abstract: 1. F1 hybrids between Secale anatolicum and six other rye “species” are heterozygous for two interchanges. Chains and rings of six at metaphase of meiosis in the hybrids show that the two interchanges involved three chromosomes.2. Relative frequencies of chains or rings of IV, V and VI vary between different F1 genotypes. This variation is correlated with genotypically controlled variation in PMC chiasma frequencies between hybrid genotypes. The lower the chiasma frequency the higher the frequencies of IVs and vice versa.3. The frequency of disjunctional arrangements, i.e. where alternate celitromeres move to opposite poles, are highest for associations of IV, least for VIs. From this it follows that the genotypes showing the highest overall disjunction per PMC are those with most IVs-namely those with low chiasma frequencies (see 2 above).4. The degree of disjunction of associations of the same length does not vary between genotypes.5. The disjunction frequencies in all associations, IVs, Vs and VIs, are very much higher than would be expected on the basis of a random orientation of centromeres.