A reference population designed for molecular genetic mapping of the chicken genome was produced by backcrossing a partially inbred Red Jungle Fowl (JF) line to a highly inbred White Leghorn (WL) line. The parental lines were chosen to maximize the expected genetic polymorphisms between them. Two full-sib F^ males, produced by crossing a JF male with a WL female, were each individually mated to about 10 WL females to produce 400 progeny. All the progeny were classified for segregation of three loci controlling color phenotype and six blood group loci, some of which have been mapped by classical methods. Segregation of these nine loci did not differ significantly from the expected 1:1 ratio with one exception. At least 20 mL of whole blood was stored from all the parents and progeny to provide DNA for molecular analysis. Screening of the parental lines and Fi crosses by Southern blot with cloned genes and by the random amplified polymorphic DNA (RAPD) procedure revealed a large number of molecular markers mat were parental line-specific. A preliminary analysis of 16 backcross progeny classified for polymorphisms at 2 color loci, 6 blood group loci, 16 loci detected by cloned chicken genes, and 4 loci detected by the RAPD method has been completed. Segregation at 27 out of 28 loci did not differ significantly from the expected 1:1 ratio, showing that two alternative alleles were detected at each locus. Five pairs of linked loci were detected (P < .01). Thus, this population is polymorphic and gives simple segregation for two types of molecular probes, providing a good resource for collaborative mapping of the chicken genome. (

We have developed an autosomal genetic linkage map of the chicken genome using a subpanel of 52 DNAs from a previously described reference backcross mapping population. The population derived from a cross of an inbred Red Jungle Fowl male and a highly inbred White Leghorn female. The backcross subpanel used was made up of offspring of a single F1 male with four White Leghorn females. Ninety-eight markers consisting of classical and erythrocyte antigen genes, restriction fragment length polymorphisms, random amplified polymorphic DNA, and chicken CR1 repeat-element polymorphisms were typed. Seventy-two of these markers were resolved into 19 linkage groups. Four of the linkage groups were assigned to chromosomes 1, 4, and 17. Four linkage groups were associated with linkage groups published earlier. Linkages within approximately 27 cM can be detected with a lod score of 3 with the panel used. The preliminary map contains approximately 590 cM within the linkage groups, and approximately 70% of the randomly selected markers fell in one of the groups; however, a considerable portion of the genome may remain outside of the existing linkage groups. These markers greatly expand the existing linkage map of the chicken genome.