In blood types, if an offspring inherits the alleles IA and IB, the offspring with have the AB blood type. This illustrates the inheritance pattern known as:

Co - dominance.

Explanation:

Co-dominance is a pattern of inheritance that do not follow the Mendelian laws. Different alleles may express themselves independent and equally express in heterozygous condition.

The inheritance pattern of AB blood group shows the co - dominance as the genes are equally dominant and express their phenotype. The allele A and allele B has equal dominance and express the phenotype of an individual blood group as AB. The multiple genes are involved in case of blood group system.

Thus, the answer is co-dominance.