When a dominant gene does not entirely mask the effects of a corresponding recessive gene, has occurred.?

Co dominant.

Explanation:

Co dominant may be defined as a type of the non Mendelian inheritance in which the alleles are not able to express themselves fully. The co dominant may occur due to the different metabolic pathway.

The co dominance is shown in the cases where the dominant gene is not able to express itself in the heterozygous condition. The heterozygous condition shows the different phenotype from the actual genotype shown by the dominant an recessive alleles.

Thus, the answer is co dominant.

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