Question

If Dave and Lisa are both heterozygous for eye color (brown is dominant, blue is recessive) what are the odds that they will have a blue-eyed baby

Answer 1

In short, the answer is 25%.
Dave and Lisa both have genotypes of Bb. Using a Punnett square, you can calculate that their child has a 25% chance of having the genotype BB, 50% chance of having the genotype Bb, and 25% chance of having the genotype bb. Translate these to phenotypes, and their baby will have a 75% chance of having brown eyes and 25% chance of having blue eyes.