Eye color is also determined by genes. Brown eyes are dominant, and blue eyes are recessive. What must be true for two brown-eyed parents to produce a blue-eyes child?

The brown-eyed parents must be HETEROZYGOUS to produce a blue-eyed child

Explanation:

This question involves a single gene coding for eye color in humans. The allele for brown eyes (B) are dominant over the allele for blue eyes (b). This means that an individual that is heterozygous (Bb) will phenotypically have a brown eyes.

According to this question, a blue-eyed child (bb) will be produced when two brown-eyed parents are HETEROZYGOUS (Bb) for the eye color trait. This means that each of the parent donated the recessive allele (b) to produce the (bb) offspring. Please find the punnet square attached.

They each pass on the blue-eye allele

Explanation:

If both parents carry a recessive blue eye gene, then it is possible for the parents to produce a blue-eyed child. The parents must be heterozygous for the eye color trait in order for this to happen. Their genotypes are not the same genes for a trait and are not (BB) or (bb) but instead (Bb). If both parents carry the recessive trait of having blue eyes, they may be able to produce a blue-eyed child.

a- all cells come from pre-existing cells