246 PHYSIOLOGIC GENETICS 



4. The uses of reciprocal crosses and other methods to investigate the nature of 

 maternal-fetal interactions influencing developmental patterns and their response to 

 teratogens. 



5. The use of inbred strains to study the intra-uterine variables that influence the 

 probability that a given embryo, predisposed by its genotype or a teratogen to be mal- 

 formed, will actually have the malformation. 



6. Study of the genetic differences in response to teratogens to clarify the inter- 

 actions of genes and extrinsic environmental agents in determining normal and 

 abnormal developmental patterns. 



