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THE ANAPHASE MOVEMENT OF CHROMOSOMES IN THE SPERMATOCYTES OF THE GRASSHOPPER

1949; Marine Biological Laboratory (MBL); Volume: 96; Issue: 1 Linguagem: Inglês

10.2307/1538001

1939-8697

Hans Ris,

Soybean genetics and cultivation

The movement of chromosomes and the changes in spindle size have been recorded in living spermatocytes of the grasshopper during the meiotic divisions. Anaphase movement consists of two separate processes which are related to the action of distinct cellular organelles: (1) The shortening of chromosomal fibers moves the chromosomes to the poles. (2) The elongation of the spindle further separates the daughter plates. The two processes act simultaneously in the grasshopper. With chloralhydrate, spindle elongation can be inhibited without affecting the action of the chromosomal fibers. This demonstrates the independence of these two factors. The effect of temperature on chromosome movement is shown by measurements at 17°, 23° and 30° C. Between 17° and 23° there is a greater increase in velocity of chromosome movement than from 23°-30° C. Temperatures above 32° C. inhibit mitosis through the destruction of the spindle. Abnormal spindle elongation is found whenever chromosomes stick at anaphase. The spindle, unable to elongate in its long axis, expands laterally into a disc-shaped body which later forms one or several finger-like processes, pushing out the cell membrane. These lateral elongations usually give rise to one or more cleavage furrows, pinching off one or, rarely, more anuclear buds. This demonstrates clearly the relationship between spindle elongation, cell elongation, and cleavage furrow. The role of the mitotic organelles in the anaphase movement of chromosomes is discussed. Indispensable for a regular anaphase are the kinetochores on the chromosomes, the chromosomal fibers, and the spindle body. No evidence was found for a specialized region in the spindle acting as "Stemmkörper." The spindle is uniform in structure and elongates uniformly. Distinct recognition of the structures involved in anaphase movement, and a quantitative description of their function, forms a basis for experimental analysis of their composition as well as their mode of action.