The Cytological Basis of Mutations

Abstract

The term mutation should be used in a generic sense to include inherited changes of any kind in the germplasm. The various types of mutations, such as trisomics, poly-ploids, translocations and gene mutations, can then be classified. Emphasis is laid upon the remarkable constancy under normal conditions in the structural arrangement and spatial relationships of the elements making up the germinal material. The term catenation is proposed for the linkage of chromosomes in rings or chains at meiosis, now known in Oenothera, Datura, Rumex and other plants. This will avoid confusion between cytological linkage and genetic linkage. The causes of catenation, especially in Oenothera, are discussed, and the theory that it arises through hybridization combined with some translocations between non-homologous chromosomes is supported. In this connection, the catenation arising in Oenothera eriensis X ammophila, O. eriensis X rubricalyx and other F1 hybrids is discussed.