A couple plans to have a child. The father is red-green colourblind (XbY) and the mother has normal vision but is a carrier (XBXb). What is the probability their child will be red-green colourblind?

Here's the completed genetic diagram and probability calculation: Parental genotypes: Person 3 (red-green colourblind male): X^b Y Person 4 (female with normal colour vision, heterozygous): X^B X^b Gametes: Person 3: X^b, Y Person 4: X^B, X^b Punnett Square: |c|c|c| Gametes & X^B & X^b \\ X^b & X^B X^b & X^b X^b \\ Y & X^B Y & X^b Y \\ Offspring genotypes: X^B X^b, X^b X^b, X^B Y, X^b Y Offspring phenotypes: X^B X^b: Normal vision female (carrier) X^b X^b: Red-green colourblind female X^B Y: Normal vision male X^b Y: Red-green colourblind male Probability of offspring having red-green colour blindness: Out of 4 possible offspring, 2 will be red-green colourblind (X^b X^b and X^b Y). Probability = (2)/(4) = (1)/(2) The probability of offspring having red-green colour blindness is 50\%. That's 2 down. 3 left today — send the next one.