Chromosomal Elimination induced by 6-Aza-Uracil

Abstract

DURING preliminary work in this Laboratory dealing with the effects of some antimetabolites on cell division in Allium cepa, it was noted that 6-aza-uracil brings about chromosomal elimination. This elimination occurred at metaphase and anaphase. Root tips from bulbs after reaching a length of 2–3 cm. were treated for 6 hr. with a 1 per cent aqueous solution. The solution was prepared by first grinding the powder and dissolving it in warm tap water. In order to clarify the location of the spindle attachment region of the chromosomes the root tips were treated with a 1 per cent aqueous solution of colchicine for a half-hour prior to fixation. On each preparation the number of normal metaphases, anaphases and telophases and the number of these stages showing elimination were counted. The eliminated chromosomes were studied in detail to determine whether or not the same chromosomes were always eliminated. Aceto-orcein smears and sections stained in iron alum hæmatoxylin were used.