Can a blue-eyed mother and a brown-eyed father have a child with brown eyes, a child with blue eyes and another with green eyes? How are genes and eye color related?
The short answer to your question is “yes, it’s possible.” There was a time when brown-eyed child born to blue-eyed parents would spark crude jokes about the milkman. But it turns out that inheritance patterns for eye color are more complicated than many people realize. Our understanding of eye color is still changing as we learn more about the processes involved.
The observable eye color of the parents doesn’t reveal the whole genetic picture. Each of the parents actually has two genes for eye color and each of their children will inherit one of the two genes from each parent. Although everyone’s DNA has two eye color genes, they don’t mix in the sense of blending colors.
A person’s eye color is determined by the eye color of the parents, the color genes of the parents and whether the genes are dominant or recessive. To confuse matters even more, there can be genetic mutations (and possibly other as-yet-unknown factors) which may give a child a different eye color outcome than what would be expected based on genes alone. There are also different shades of eye color and different ways in which the pigment is distributed.
We describe the eye color gene pairs as homozygous, meaning two of the same color gene, or heterozygous, meaning two different color genes. The observable traits are the phenotype, while the actual genetic makeup is called the genotype.
I don’t think I’d bet money on the scenario you describe, but the bottom line is that it can happen. All our charts and mathematical calculations for hereditary outcomes are based on likelihood and as we’re still learning, the eye color genes don’t always follow the rules.