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  •  The ABO blood type in humans is under the control of autosomal multiple alleles. Color blindness is a recessive X-linked trait. A male with a blood type A and normal vision marries a female w

 The ABO blood type in humans is under the control of autosomal multiple alleles. Color blindness is a recessive X-linked trait. A male with a blood type A and normal vision marries a female who also has blood type A and normal vision. The couple’s first child is a male who is color blind and has O blood group. What is the probability that their next female child has normal vision and O blood group?

 

Option: 1

 1/4


Option: 2

3/4


Option: 3

1/8


Option: 4

1


Answers (1)

best_answer

In this scenario, the male is blood type A and has normal vision, while the female is also blood type A and has normal vision. Their first child is a male who is color blind (a recessive X-linked trait) and has O blood group (recessive allele). We want to determine the probability that their next female child has normal vision and O blood group.

Let's consider the inheritance of these traits separately:

Blood group:

The male parent is blood type A, which means he has at least one allele for blood type A (IA). The female parent is also blood type A, so she also has at least one allele for blood type A (IA). Since blood type A is dominant, both parents must have at least one A allele. The child being O blood type means that he inherited an O allele (i) from both parents. Therefore, both parents must be heterozygous for blood type (IAi). The probability of their next child (female) having O blood group is 1/4 (since there is a 1/2 chance of inheriting the O allele from each parent).

Vision (color blindness):

The male parent has normal vision, which means he does not carry the recessive allele for color blindness (XN). The female parent also has normal vision, so she does not carry the recessive allele (XN). However, their first child is a male who is color blind, which means he inherited the recessive allele for color blindness (Xn) from his mother. The male child received the X chromosome from his mother, which carried the Xn allele. Since the mother is not color blind, she must be heterozygous for color blindness (XNXn). The probability of their next child (female) having normal vision is 1/2 (since there is a 1/2 chance of inheriting the normal vision allele XN from the mother).

To calculate the probability that their next female child has normal vision and O blood group, we multiply the probabilities for each trait:

Probability of normal vision (1/2) \times Probability of O blood group (1/4) = 1/8

Therefore, the probability that their next female child has normal vision and O blood group is 1/8.

Hence, the correct answer is option 3.

Posted by

Pankaj Sanodiya

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