Symposium on Animal Genetics: XI11 International Congress of Genetics MOLECULAR AND REPRODUCTIVE BIOLOGY IN ANIMAL GENETICS

ROCEDURES in molecular and reproductive biology off er exciting new OSPsibilities for the animal geneticist. In addition, many molecular biologists are now directing their expertise and techniques toward problems in animal genetics. Through the characterization of deleterious and normal gene expression an increased selection efficiency may be obtained along with an understanding of gene-environmental interactions and single gene contributions to phenotypic development. Examples of developments in these areas which have a place in animal genetics include: a) The electrophoretic separation of proteins has had a definite influence on our approach to gene frequency studies in laboratory and wild animal populations (see HUBBY and LEWONTIN 1966). b) Blood group analysis has been a very important tool in studies of gene drift in isolated populations of man (see MOTULSUKY 1970). Blood constituents may also be useful gene markers. For example, there is evidence that the B locus is associated with disease resistance and other economic traits in the chicken ( BRILES and ALLEN 1961 ) . c) Somatic cell genetics, based on interspecies cell chimeras and the fusion of different cell lines within a single species, has permitted significant advances to be made in animal and human gene mapping in recent years (see EPHRUSSI 1972). d) Chromosome banding techniques including the development of fluorescence, Giemsa and DNA banding patterns in chromosome analysis has permitted positive identification of homologs (LIN et al., 1973). e) Genome organization-the concept that the mammalian genome consists of a mixture of repeated and single copy DNA base sequences was introduced by BRITTEN and KOHNE (1968). This concept, based on the reassociation kinetics of denatured DNA and described by Cot, has been the basis for numerous evolutionary studies (see MCCARTHY 1973). f ) The transcriptional unit has been defined by RNA/DNA reassociation studies in estimations of the complexity of RNA transcription in differentiating tissues. The structure and processkg of the heterogeneous RNA synthesized at a transcriptional unit is discussed by PAUL and FIRTEL (1973; CHURCH and SCHULTZ 1973). Examples of concurrent developments in reproductive biology which may have