C. INDIVIDUAL TRAIT ANALYSIS AND THE 

 PHYSIOLOGY OF GENE ACTION 



The third objective of NE-6 was the analysis of individual traits and 

 to interpret the type of gene action involved with special reference to 

 metabolic and endocrine effects. 



Genes produce their effects in many ways. Some genes affecting 

 plumage color, for example, seem to produce large and dramatic primary 

 effects simply and directly. On the other hand, some traits such as egg 

 production seem to be influenced by many genes, each of which has 

 small effects which in turn may be mediated through the endocrine 

 system or other physiological pathways. Several contributing projects 

 to NE-6 were directed toward this third objective. 



Plasma Proteins 



In four separate trials of 27 to 30 birds each, plasma proteins of 

 individual female chickens from the Connecticut randombred popula- 

 tion were separated into 15 fractions by researchers of the Connecticut 

 Agricultural Experiment Station (41). Analyses of total protein or 

 levels of the 15 protein fractions with five economic traits showed no 

 consistent correlations. However, analyses between total protein or levels 

 of the 15 protein fractions and four indices describing state of pro- 

 ductivity near the time of blood collection did show consistent corre- 

 lations. Protein components F and G repeatedly showed close relation- 

 ships with all four indices of productivity (number of days since last 

 egg, seven-day production before bleeding, 14-day production before 

 bleeding, and seven-day production before and after bleeding) . Also, a 

 relationship was suggested between the amount of component L and 

 some of the productivity measurements. These data suggest a functional 

 relationship between some of the chromatographically distinct plasma 

 protein components and the short term dynamic and complex metabolic 

 systems concerned with egg productivity. 



Plumage Color 



Some genes which primarily determine feather colors and patterns 

 influence other traits as well, i.e., their action is j)leiotropic. At the Mass- 

 achusetts Agricultural Experiment Station populations homozygous for 

 recessive white were established which were segregating for alternate 

 alleles at five different loci. The use of suitable testing procedures re- 

 vealed that the gene E was associated with greater mortality, including 

 more leucosis, than its allele c^ for three consecutive generations. Birds 

 possessing the genotype li' or Ee^ were superior to their / ' t i flock- 

 mates with respect to survivor egg production and to hen-caged egg pro- 

 duction for several generations. However, this relationship disappeared 

 after the F5 generation. 



In another experiment designed to examine pleiotropic effects of 

 plumage color genes, it was found that colored ])irds( C"i r) were heavier 

 at 8 weeks of age than their recessive white sibs (cc) (48, 49). When 

 the C'^C' and C'c genotypes were compared with cc genotypes, the 

 results indicated no superiority for either the hetcrozygote or the homo- 

 zygous dominant group. It was not determined whether these resxilts 



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