4-72 GENETICS OF SOMATIC CELLS 



The rudiments for mammalian somatic-cell genetics have been accumulating during 

 this past decade; additional progress can stem from the employment of more distinctive 

 lines of cells than those currently in use. 773 To Lederberg's plea can be added the 

 need for karyotypic control as a major critique when evaluating newer forms as poten- 

 tial replacements of the more cumbersome types of cells. 



REVIEW OF TECHNIQUES 



There have been extensive technical advances in preparing slides. In addition, 

 slide preparation may involve personal embellishments, as becomes evident to the user 

 in trying to duplicate a particular technique. At times, independent laboratories have 

 similar difficulties after following accurately the step-by-step procedures described by 

 the originator. Generally speaking, the number of techniques is increasing, primarily 

 because of the need to assure the maximum number of mitoses, especially for cells 

 having limited viability or mitotic activity and cytoplasmic volume. The increasing 

 numbers of investigators conducting mammalian chromosomal studies are certain to 

 evaluate the various published procedures quite thoroughly and, in turn, devise addi- 

 tional variations on this subject. If this follows, it will serve to illustrate the ever 

 widening applications of cytogenetic principles and approaches to more distant areas 

 of research. 



The procedures outlined by Ising, 643 Makino and Sasaki, 842 and Hansen- 

 Melander 520 serve equally well as sources of earlier cytologic techniques for ascites- 

 tumor cells. Persons interested in chromosomes of solid tumors (primary or 

 transplantable) will find the approaches of Bayreuther and Klein 64 and Hungerford 614 

 most helpful. Methods of tissue culture have become quite varied. Cellular types 

 vary considerably in squashing properties, and special pretreatments and procedures 

 have been promoted to emphasize the clarity of the individual chromosome. These 

 different approaches serve to illustrate the durability of cultured cells when handled 

 properly. For tissue-culture procedures, other than those outlined in this chapter, the 

 reader will find variations of the general theme and approaches by Puck et al., 1028 

 Hsu and Klatt, 605 Ruddle et a/., 1084 Levan and Biesele, 782 Awa et al.* 1 and Ford and 

 Yerganian. 391 For those who have recently joined the ranks, the air-dry schemes of 

 Rothfels and Siminovitch, 1077 Tjio and Puck, 1322 and Moorhead et al. 893 will provide 

 ample encouragement. For bone marrow, the procedures of Ford and Hamerton 386 

 are certain to be satisfactory for many species. 



At times, the minute, and occasionally extensive, listing of details of some pro- 

 cedures will indicate the multiplicity of trials which the individual investigator has 

 conducted to prepare chromosomes for viewing. Since much depends on the in- 

 dividual's skill during any phase of carrying out his procedures, rigid adherence to any 

 one schedule by the novice may result in failure. If unsuccessful after numerous 

 attempts, he should proceed to another method and, if necessary to satisfy his own 

 ability and requirements, select and combine those steps which appear to enhance the 

 material in use. 



