COMPARATIVE-ANALYSIS OF AVIAN-LEUKOSIS VIRUS-RELATED ENDOGENOUS VIRALGENES IN EXPERIMENTAL STRAINS OF THE DOMESTIC CHICKEN

DNA sequences related to avian leukosis virus (ev genes) were identifi ed in the genome of chickens from 6 experimental strains including 3 r andombred lines (Wyandotte, Fayoumi and White Leghorn), 2 divergently selected Rhode Island Red lines and a synthetic broiler line. Digestio n of genomic DNA with Sad and BamHI enzymes and hybridization with eit her RAV-2 sequences or an LTR-gag probe revealed 66 different Sad band s, 53 of which could be associated with particular BamHI bands such th at the ev loci could be defined at the molecular level. The distributi on patterns were very strain-specific. Average band frequency and hete rozygosity level could be correlated with the genetic history of the l ines and their inbreeding level which varied from 0.04 to 0.28. Within -family segregation did not show any allelic relationship between retr oviral insertions that were considered to be 2 genes. The Fayoumi line showed the largest variation in ev number per bird and contained a fe w birds free of any endogenous viral sequences, designated ev0. The br oiler line showed the highest ev number. Very few ev loci were shared by different lines; only ev6 was found in all strains. Comparison with the established classification in White Leghorns was not straightforw ard and further analysis of DNA polymorphism and viral expression is n eeded.