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Mahesh (who is colourblind) and Soni (who is not colourblind) have a daughter Alia. Rishi (who is not colourblind) and Neetu (who is a carrier) have a son Ranbeer. Alia and Ranbeer get married. What is the probability that their daughter will be colourblind?
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25 %
The genotype of Alia will be XXc since she receives only one Xc chromosome (colourblindness chromosome) from her father. Ranbeer may be XY or XcY (since his mother is a carrier).
So we consider two possibilities:
1 . Alia XXc and Ranbeer XY. In this, the daughters could be XX (not colourblind) or XXc (not colourblind)
2 . Alia XXc and Ranbeer XcY. In this, the daughters could be XXc (not colourblind) or XcXc (colourblind)
Thus there is only 1 in 4 chance that their daughter will be colourblind.
So we consider two possibilities:
1 . Alia XXc and Ranbeer XY. In this, the daughters could be XX (not colourblind) or XXc (not colourblind)
2 . Alia XXc and Ranbeer XcY. In this, the daughters could be XXc (not colourblind) or XcXc (colourblind)
Thus there is only 1 in 4 chance that their daughter will be colourblind.
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