For hair color, having dark/brunette hair is dominant to having light or blond hair. Olivia Keller is blond but her mother, Mrs. Keller is brunette. Mr. Keller is also brunette. Use a Punnett Square to show whether Olivia could be the Kellers’ daughter.

Olivia could be the Keller's daughter if both parents are heterozygous for their brunette hair coloration. Please find the punnet square in the attachment section.

Explanation:

According to this question that involves a gene coding for hair color in humans, the allele for dark/brunette hair (B) is dominant to the allele for light/blond hair (b). This means that a heterozygous individual (Bb) will have a brunette hair coloration.

Olivia Keller is said to have blond hair but her mother, Mrs. Keller and father, Mr. Keller both have brunette hair coloration. Since Olivia is blond (recessive), she must have a genotype "bb". However, this is possible if both of her parents i.e. Mr and Mrs. Keller have a heterozygous genotype (Bb).

From the punnet square of the cross, Bb × Bb, in the attachment section, it can be observed that brunette color (BB, Bb, Bb) and blond color (bb) were produced in the offsprings in the ratio 3:1. This means that it is very likely that Olivia could be the Keller's daughter.