DNA sequence analysis of a class I gene (QlO), which maps to the Qa2,3 locus in the C57BL/lO (H-
2b haplotype) mouse, reveals that it is almost identical
to a cDNA clone (pH16) isolated from a SWR/J
(H-2q haplotype) mouse liver cDNA library. Exon 5,
in particular, has an unusual structure such that a
polypeptide product is unlikely to be anchored in the
cell membrane. Our findings suggest that the two
sequences are derived from allelic class I genes,
which are nonpolymorphic, in contrast to H-2K allelic
sequences from the same mice, and they may encode
liver-specific polypeptides of unknown function.
Our previous studies indicate that the QlO gene
is a potential donor gene for the generation of mutations
at the H-2K locus by inter-gene transfer of
genetic information. Thus the lack of polymorphism
in class I genes at the QlO locus implies either that
they are not recipients for such exchanges or that
selective pressure prevents the accumulation of mutations
in genes at this locus