IgA is the principal class in secretions, the most important being those from the epithelia lining the intestinal and respiratory tracts.

Dimeric IgA operates mainly on epithelial surfaces.

This monomeric IgA is predominantly of the subclass IgA1; the ratio of IgA1 to IgA2 in the blood is 10:1.

IgA antibodies produced by plasma cells in the gut are dimeric and predominantly of subclass IgA2; the ratio of IgA2 to IgA1 in the gut is 3:2.

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#Unit 8. Inheritance Biology

Supplementary genes:

Two independent dominant genes interacting to produce a phenotypic expression different from that produced by either gene alone.

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Supplementary gene interaction (9:3:4)

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DOMINANT EPISTASIS

In dominant epistasis, however, only a single copy of an allele is required to inhibit the expression of an allele at a different locus.

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DUPLICATE RECESSIVE EPISTASIS(9:7): Duplicate recessive epistasis, in which two recessive alleles at either of two different loci can suppress a phenotype.