Isozymes and the Maternal Effect

Tadpole, 3 days Tadpole, 11 days Adult, 3 months Total 

1968) esterases (Korochkin et al., 1973 b). The maternal spectrum of the previously listed enzymes was already formed in the oocyte. These genes are nonactive until a certain stage of development subsequent to their activity in the oocyte stage. 

There are several possible causes which could affect the differential phenotypic expression of enzymes in early development- the maternal effect. Among these are (1) the stability of enzyme accumulated during oocyte maturation (2) the stability of mRNA s which code for the maternal subunits of enzyme (3) the comparatively early activation of maternal genes as opposed to paternal genes. 

Apparently, either mechanism could predominate in different species and in different stages of evolutionary development. 

Recently Gerasimova obtained new data connected with the previously discussed problem (personal communication). She investigated the activity of the maternal isozyme of 6-phosphogluconate dehydrogenase in Drosophila progeny from crosses 

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