Enzyme expression in fish. There are several examples of repression of specific parental enzyme alleles, some of which may be
attributable to inter-species effects. For example, the paternal allele of 6-phosphogluconate dehydrogenase was repressed at a
specific developmental stage of Cyprinid fish (Rutilus rutilus) (Klose J et al, 1970). Transient repression of the maternal
isozyme of alpha-glycerophosphate dehydrogenase was observed in offspring from a female brown trout and a male brook trout,
but not for the reciprocal cross (Schmidtke J et al, 1976). Repression of the maternal allele
of glucose 6-phosphate dehydrogenase, maternal allele a liver esterase, and repression of a paternal esterase has been observed in
intertribal or interspecific sunfish hybrids (one directional crosses only) (Whitt GS, J.Exp.Zool. 1972;179:271-282; Whitt GS, J.Hered.