Satellite DNA III and alkaline Geimsa staining.

Satellite DNA III visualized by staining chromosomes with Giemsa at pH 10-12. Evidence is presented that besides the secondary constriction of chromosome 9, satellite III contained in considerable amount in the long arms of chromosome 20, giving rise to a clearly visible secondary constriction just below the centromere. The latter finding confirms that reported by Bobrow et al. (1972). The long arms of the Y chromosome also show strong staining with alkaline Giemsa, the region of staining corresponding exactly with the intensely flourescing area. This is interpreted as possible evidence for the presence of satellite DNA III in the distal long arms of the human Y chromosome.