Intragenic DNA spacers interrupt the ovalbumin gene

The authors have performed restriction endonuclease mapping to examine the linear organization of the ovalbumin gene in chromosomal DNA. Treatment of genomic DNA with restriction endonucleases that do not cleave the ovalbumin mRNA sequence results in the generation of multiple DNA fragments capable of annealing with ovalbumin-specific probes in molecular hybridization reactions. These data strongly suggest that the linear order of DNA sequences coding for ovalbumin is interrupted by at least two intragenic DNA spacers absent from the corresponding RNA. At least one of these spacer sequences interrupts the coding sequence; therefore the chromosomal ovalbumin gene is not colinear with its translational product. We can discern no difference in the sequence organization about this gene in producer and nonproducer somatic cells, suggesting that the presence of intragenic spacers does not reflect that transcriptional activity of this gene. Furthermore, profiles obtained for gametes are identical to those observed for somatic cells, indicating that significant translocation during development is not responsible for the generation of this split sequence. Divergence of the intragenic spacer, however, is observed between individual chickens; thus multiple alleles may exist for this gene that are identifiable by differences in the organization of spacer with no apparent phenotypic evidence for their presence.