Question

1. brown eyes (b) are dominant over blue eyes (b). using this example, explain how a child can have a trait that neither parent expresses physically. use a punnett square to validate your answer.

Explanation:

Step1: Determine the parents' genotypes

Since brown eyes (B) are dominant over blue eyes (b), and the parents don't show the blue - eye trait (but can have a child with blue eyes), the parents must be heterozygous. So the parents' genotypes are \(Bb\times Bb\).

Step2: Create the Punnett square

	B	b
b	\(Bb\)	\(bb\)

The Punnett square shows the possible combinations of alleles from the parents.

Step3: Analyze the offspring genotypes

From the Punnett square, the possible genotypes of the offspring are \(BB:Bb : bb=1:2:1\). The \(bb\) genotype represents the blue - eye trait. Even though the parents (\(Bb\)) have brown eyes (because of the dominant \(B\) allele), they can pass on the recessive \(b\) allele. When both parents pass on the \(b\) allele (\(b\times b\)), the child will have the \(bb\) genotype and express the blue - eye trait (a trait not expressed by the parents).

Answer:

If both parents have the heterozygous genotype \(Bb\) (brown - eyed), using the Punnett square \(Bb\times Bb\) gives a \(25\%\) chance (\(bb\)) for the child to have blue eyes. So a child can have a trait (blue eyes) that neither parent expresses physically because the parents carry the recessive allele (\(b\)) and can both pass it on to the child.