An Interchange in Maize Giving Low Sterility and Chain Configurations

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Abstract
A case of partial sterility characterized by low sterility (about 25%) and a chain of 4 chromosomes at diakinesis in meiosis is described and shown to be due to an interchange of non-homologous parts. The longest chromosome and the satellite chromosome, corresponding to the P-br and the Y-Pl linkage groups respectively, are involved in the chain. Mid-prophase studies show that the terminal 1 or 2 chromomeres of the satellite had been interchanged with about 3/4 of the longer arm of the P-br chromosome. The figures approximate a T-shaped configuration due to the fact that the ends of the satellite do not synapse to complete the cross-shaped complex found in other interchanges. Metaphase distribution of these chromosomes is such that 50% sterility would be expected if both types of deficiencies result in aborted spores. Tests show that one type may survive, thus accounting for the 25% sterility in place of the expected 50%. This case demonstrates that many features expected to accompany simple translocation may be the result of an interchange.