THE ORIGIN AND CONSEQUENCES OF SUBCHROMATID ABERRATIONS INGASTERIA ERNESTII-RUSCHII

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Abstract
Cytological studies of a plant of Gasteria ernestii ruschii Dtr. revealed the presence of anaphase I bridges with side arms which are usually unaccompanied by fragments. The fragments, when present, were of no regular size and ranged from very small to very large ones. The presence of only fragments or bridges at anaphase II and the above described behaviour of anaphase I chromosomes indicates the presence of subchromatid breakage and reunion. The cytological and genetic consequences of such aberrations are discussed. In a few cases two large chromosomes were interpreted to divide equationally as univalents at metaphase I. Since no univalents for large chromosomes were observed at stages prior to metaphase I their presence may be attributed to 'abortive terminalization' resulting from subchromatid breakage.