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Why can two parents with brown eyes have a child with blue eyes in a simplified inheritance model?

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Four kittens with different fur patterns-three tabby and one black-and-white-lying together in a box, illustrating genetic variation among offspring. — heredity Each offspring is a combination of its two parents, receiving some dominant traits from its mother and others from its father.

In a simplified model of heredity, brown eye colour is considered dominant over blue eye colour. Under this Mendelian framework, an individual possesses a pair of alleles for a trait—one inherited from each parent.12

If both parents have brown eyes but carry a hidden recessive allele for blue eyes, they are considered heterozygous for the trait. In this scenario, each parent can pass on either the dominant brown allele or the recessive blue allele to their offspring. If a child inherits the recessive blue allele from both parents, they will express the blue eye phenotype, despite both parents having brown eyes.21

It is important to note that while this simplified model illustrates the basic principles of dominant and recessive inheritance, the actual genetics of human eye colour is far more complex, involving multiple genes that interact to determine the final pigmentation and appearance of the iris.1