The major and minor chicken vitellogenin genes are each adjacent to partially deleted pseudogene copies of the other.

The major chicken vitellogenin gene (VTGII) has previously been cloned and sequenced. We now report the isolation of genomic clones that encompass a minor chicken vitellogenin gene (VTGIII) which is also expressed in the liver in response to estradiol. Our analysis reveals that a pseudogene for VTGII (psi VTGII) lies 1,426 base pairs upstream of this VTGIII gene. A reevaluation of published sequence data reveals that the converse is also true, namely, that a pseudogene for VTGIII (psi VTGIII) lies 1,345 base pairs downstream of the VTGII gene. Our results show that a 335-base-pair deletion has removed the psi VTGIII promoter and cap site but left residual estrogen response element in a region where nuclease-hypersensitive sites have been reported to be induced in response to estradiol.