Biochemical evidence for the existence of a null allele at the leucine aminopeptidase-2 (Lap-2) locus in the oyster Crassostrea virginica (Gmelin)

Abstract

The existence of a null activity allele at the leucine aminopeptidase-2 (Lap-2) locus in the oyster Crassostrea virginica (Gmelin) was previously inferred from anomalous segregation patterns observed in offspring from pair crosses, and from the occurrence of individuals lacking Lap-2 bands on gels (presumed null homozygotes). The present research was done to determine whether leucine aminopeptidase specific activity was significantly reduced in oysters presumed from breeding experiments to be heterozygous for a Lap-2 null allele. Approximately thirty 4-month-old oysters from each of two crosses were analyzed. In each cross, LAP specific activity was significantly reduced (P < 0.001) in active/null heterozygotes, compared with full-sib oysters that were active/active heterozygotes. On average, active/null heterozygotes had 57% of the activity of the corresponding active/active heterozygotes.Key words: oysters, null allele, leucine aminopeptidase.