The phenotype of the fish when both R and Bl are present will be Blue and Red while the genotype will be BR.
Co-dominance in genetics is the condition in which alleles of a gene are both dominant in that when both are present in an organism, the organism will show the phenotype of both alleles.
Since the alleles B for blue coloring, and R for red coloring are both dominant, when both are present in the fish, the phenotypic coloring in the fish will be blue and red.
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