Could two blue‑eyed parents have brown‑eyed children? Why? (Use a Punnett square to demonstrate your answer, and state whether the children will be heterozygous, homozygous recessive or homozygous dominant.)

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No, two blue eyed parents could not have a brown eyed child. The reason for this is because the blue eyed gene is recessive, and the brown eyed gene is dominant. The only way for a person to be phenotypically blue eyed is for that person to have both recessive genes in their genotype.

In a Punnett square, you can represent the dominant and recessive versions of a gene with a single letter that is either capitalized or lower case. A capital "B" is dominant, and a lower case "b" is recessive. "B" represents the dominant brown eye color, and "b" represents the recessive blue eye color. Any parent that has blue eyes is genotypically "bb." This means that the only gene that this person could donate is the recessive "b." If both parents are guaranteed to donate the recessive allele, then the child is guaranteed to inherit two recessive alleles. The "bb" option will guarantee a blue eyed child, and since neither parent has a dominant brown eye gene "B" to donate, then there is no chance for these particular parents to produce a brown eyed child. Because the child is "bb," we would say that the child is homozygous recessive. Homozygous means that the same version of the gene is present, and recessive identifies which version is present.

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