PREFACE 



Information recently acquired about the biochemistry of heredity has increased 

 the likelihood of determining precisely how the more formal transmission of genetic 

 information is accomplished in higher organisms and has imposed the obligation to 

 renew the task of controlling changes in composition, propagation, and action of the 

 genetic material. The complexity of mammalian genesis and development is regarded 

 no longer as a barrier to investigation at the molecular level, but more as an opportunity 

 to study mechanisms that do not exist in lower organisms in relation to common 

 hereditary units and to choose between alternate explanations for a given process. 

 Possibly the greatest advantage the laboratory mammal offers is not only the possibility 

 of developing strains of animals having remarkably similar partial or total genome 

 but also the opportunity to breed representatives from diverse strains in a manner 

 appropriate for the elucidation of genetic mechanisms. In addition, these uniform 

 lines are available for comparison of the genetic behavior of cells with known properties 

 in vivo and in vitro. Recent evidence for fusion of mammalian cells in vitro suggests 

 that the analytical advantages of sexual reproduction may be extended to studies of 

 the somatic cell as well. Also, the many hereditary diseases known to occur in inbred 

 mammals and the varied response of different strains to bacterial, viral, and parasitic 

 inoculation offer means to determine parameters that may also be operable in similar 

 diseases in man. 



A host of methods have been evolved for providing stocks of mammals with 

 uniform genotype suitable for given experimental objectives. The theoretical and 

 practical aspects of insuring this type of control and some indication of how methodology 

 from other scientific disciplines may be used in mammalian genetics are mandatory 

 for an approach to the solution of problems that engage the attention of many con- 

 temporary investigators. The intent of the contributors to this volume is to provide 

 a selected array of methods applicable to mammalian genetics that may prove useful 



