Gray-colored offspring are produced when a black bird and white bird of a certain species are crossed. what would be the predicted phenotypes of the offspring if two gray birds are crossed, providing the color is determined by just two alleles?

Three types of phenotype will be produced. One is grey, second is black and third is white.

The color is controlled  by two alleles. Lets suppose B is dominant allel and b is recessive allele.

The black color organism has genotype BB and white bb.

The grey color is the indication of incomplete dominance and the genotype is Bb.

When two Bb will crossed:

Bb × Bb = 1/4 BB, 1/2 Bb , 1/4 bb.

So the 50 % chances are of grey organisms and 25 % of white and 25% of black.

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