The a-specific genes are activated by the MCM1 (Minichromosome maintenance protein 1) protein that binds and transcribes the genes in a-cell. α-specific genes are inactive even in the presence of MCM1 genes as the requisite helper proteins are not present in the a-cells.
But in the case of an α-cell, the protein MCM1 is repressed by the presence of α2 protein, thus preventing the a-specific genes from being expressed. Another protein α1, when binds with MCM1 protein activates the α-specific genes in α-cell. In the case of a a/α cell the a-specific gene is repressed by the presence of α2 protein that acts on the MCM1 proteins from activation. Since, α1 protein is absent in the a/α cell, the α-specific gene is also prevented from expressing. Also the presence of the complex a1/a2 prevents the activation of the α-specific genes due to the absence of α1 and α2 proteins.