The Fusion of Broken Ends of Chromosomes Following Nuclear Fusion

Abstract

In Zea mays, chromosomes with broken ends can be produced by a method involving an abnormal chromosome 9 with a duplication of the short arm, leading to the formation of dicentric chromatids that break during a meiotic anaphase. After a series of chromatid fusions and breakages in gametophyte mitoses, all nuclei of the mature gameto-phyte possess one chromosome with a broken end. Crosses where one or all gamete nuclei possess broken-ended chromosomes indicate that 2 chromosomes do not have to be in contact or even in the same cell at the time of breakage for subsequent fusion of their broken, "unsaturated," ends. The ability of broken ends to fuse does not last indefinitely. "Healing" may occur without fusions even when 2 broken ends are in the same nucleus.