NEET Sample Paper NEET Sample Test Paper-14

  • question_answer Red-green colour blindness in humans is governed by a sex-linked recessive gene. A normal woman whose father has colour blindness marries a colour blind man. What proportion of their daughters is expected to be colour-blind?

    A)  3/4                

    B)  1/2

    C)  1/4                

    D)  All

    Correct Answer: B

    Solution :

    Normal woman whose father was colour blind would have received the X chromosome from her father \[\to {{X}^{c}}X-\] marries a colour blind man \[-{{X}^{c}}Y\to \] their progeny. \[\begin{align}   & \,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\underset{\downarrow }{\mathop{{{X}^{c}}X\times {{X}^{c}}Y}}\, \\  & \text{Progeny}\,\,\,\underset{\begin{smallmatrix}  colour\,blind \\  daughter \end{smallmatrix}}{\mathop{{{X}^{c}}{{X}^{c}}}}\,\,\,\underset{\begin{smallmatrix}  normal \\  daughter \end{smallmatrix}}{\mathop{{{X}^{c}}X}}\,\,\,\underset{\begin{smallmatrix}  colour\,blind \\  son \end{smallmatrix}}{\mathop{{{X}^{c}}Y}}\,\,\,\underset{normal\,son}{\mathop{XY}}\, \\ \end{align}\]


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