A) 0
B) 0.0626
C) 0.125
D) 0.26
Correct Answer: C
Solution :
[c]A normal red-green colour vision man with \[R{{h}^{-}}\] blood group is \[XY\,R{{h}^{-}}R{{h}^{-}}.\] A normal woman with \[R{{h}^{+}}\] blood group with heterozygocity at both red-green colour vision and blood group is\[X{{X}^{C}}R{{h}^{+}}R{{h}^{-}}.\] |
The inheritance of colour vision in the progeny is |
i.e., 50% boys are colourblind also 50% of offspring are boys. Thus, 0.25 is the probability the first boy is colourblind. |
The inheritance of Rhesus blood group in the progeny is |
i.e., 50% are Rhesus positive and 50% Rhesus negative or 0.5 is the probability of the progeny being Rhesus negative. |
Probability of their first child being a rhesus negative = 0.5. |
Probability of their first child being a red green colourblind boy =0.25. |
Therefore, probability of their first child being both \[=0.5\times 0.25=0.125.\] |
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