Linkage analysis of endogenous viral element 1, blue eggshell, and pea comb loci in chickens

Linkage analyses were conducted among endogenous viral element 1 (ev1), pea comb (P), and blue eggshell (O) loci, mapped to the short arm of chromosome 1 in chickens. The F-1 males were produced from a cross between pea comb Araucana males negative for ev1 and known to be homozygous at the blue eggshell locus, and single comb White Leg horn females positive for ev1 and laying white shelled eggs. Recombination data were based on birds from a test cross of three F-1 birds, each mated to 10 single combed, brown eggshell laying Rhode Island Red (RIR) hens, negative for ev1 integration. Birds were screened for ev1 by DNA amplification using the polymerase chain reaction (PCR). Analyses of 207 progeny segregating for linkage between ev1 and P showed an estimated average map distance of 4.0 cM. Linkage analyses based on 44 progeny resulted in estimates of map distances of 1.8 and 4.1 cM between ev1 and O and P and O loci, respectively. Based on these estimates, the order of these three loci on the short arm of chromosome 1 can be inferred to be centromere, P, ev1, and O.