A Correlation of Ring-Shaped Chromosomes with Variegation in Zea Mays

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Abstract
Pollen carrying the dominant allelomorphs of genes affecting plant pigmentation was x-rayed and placed upon the silks of recessive plants. This was done for the b, pl, and bm 1 loci. Certain F1 individuals were mosaics, i.e., showed a variegation composed of the dominant and recessive color types. These variegated plants possessed a ring-shaped chromosome. Since the ring chromosome varied in size in different cells, sometimes being totally eliminated, it was argued that the variegation was caused by the somatic elimination of that part of the ring chromosome which carried the dominant allelomorph. Occasionally the size and the number of ring chromosomes increased. However, only ring chromosomes arose from ring chromosomes. Studies of the synapsis and morphology of the different ring chromosomes and their normal homologues at the mid-prophase of meiosis gave the approximate location of the b and pl loci. The gene b is situated in the mid-portion of the short arm of the B-lg chromosome. The locus of pl is towards the middle of the long arm of the satellited chromosome.

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