The Central Problems of the Biochemistry of 

 Cell Division 



Daniel Mazia 



Department of Zoology, L nirersitv of Ca/ifornia, 

 Berkeley,' Calif., U.S.A. 



The frame of reference for any consideration of cell division is the 

 whole cell. Entering division, it acquires poles and an equator. When we 

 contemplate the reproduction and distribution of the genetic equipment 

 in the mitotic cvcle, we can no longer confine ourselves to questions 

 concerning the molecular character of genetic information, but now must 

 consider how it is packaged into chromosomes. The problems of the 

 chromosome involve us in behaviour and mo\ement, and not merely the 

 control of biosynthesis. The movements are rapid and orderlv ; the 

 distances travelled are very long by molecular standards. The cell as a 

 whole divides itself in a way that is consistent both in timing and in 

 geometry. At the end of the cycle, we have two full-fledged cells, each with 

 the capacity for living its own pri\ate life, where previouslv we had one. 

 The whole operation of cell division is not only a large-scale operation, 

 being played on a cellular stage in micron dimensions, but is also a purpose- 

 ful one in an intelligible and unpanglossian sense. 



Having to deal with these problems of large-scale structure, of large- 

 scale polarity, with complex but sensibly co-ordinated movements, and 

 with precise timing, the student of cell division does not have to be 

 reminded of the need to correlate Biological Structure and Function, the 

 theme of this Symposium. The correlations are built into his every problem. 



I hope that this introduction, which has been intended as a descriptive 

 characterization of the problem of cell division, is not interpreted as an 

 apology for its difficulty or complexity. Of course, cell division is complex 

 in a sense in which a single biosynthetic step, for example, is not, but it is 

 an analyzable complexity. We can analyze it into unit processes which are 

 not quite so formidable in themselves. Such an analysis has recently been 

 discussed by me [i]. The difficulties are real, but we may take the opti- 

 mistic view that they arise chiefly from our lack of a biochemistry of 

 structure and of multimolecular phenomena. This could hardly have been 

 asked of the infancy or adolescence of biochemical science, but we mav 

 now expect it from its maturity. 



