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A couple had two sons, one was colour bl...

A couple had two sons, one was colour blind while the other wasn't. They also had a colour blind daughter. Which statement about this couple is true?

A

Husband is colour blind but wife is not

B

Husband is normal and wife is colour blind

C

Husband and wife both are colour blind

D

Husband and wife both are normal

Text Solution

AI Generated Solution

The correct Answer is:
To solve the problem, we need to analyze the genetic inheritance of color blindness, which is a sex-linked recessive trait primarily carried on the X chromosome. ### Step-by-Step Solution: 1. **Understanding Color Blindness Inheritance:** - Color blindness is caused by a recessive allele located on the X chromosome. - Males have one X and one Y chromosome (XY), while females have two X chromosomes (XX). - A male will be color blind if he has the allele on his single X chromosome (XcY), while a female must have the allele on both of her X chromosomes (XcXc) to be color blind. 2. **Analyzing the Family:** - The couple has two sons: one is color blind (XcY) and the other is not (XY). - They also have a color blind daughter (XcXc). 3. **Determining the Parents' Genotypes:** - Since one son is color blind, he must have inherited his X chromosome with the color blindness allele from his mother. - The normal son must have inherited a normal X chromosome from his mother. - The color blind daughter must have inherited one color blind X chromosome from each parent. 4. **Evaluating Each Statement:** - **Statement 1:** Husband is color blind (XcY) and wife is not (XX or XcX). - This is possible. The wife could be a carrier (XcX) or normal (XX). This scenario allows for the progeny to have one color blind son (XcY), one normal son (XY), and one color blind daughter (XcXc). - **Statement 2:** Husband is normal (XY) and wife is color blind (XcXc). - This cannot be true because if the wife is color blind (XcXc), all children (sons and daughters) would inherit at least one Xc, making them all color blind. - **Statement 3:** Both husband and wife are color blind (XcY and XcXc). - This cannot be true because all children would be color blind. - **Statement 4:** Both husband and wife are normal (XY and XX). - This cannot be true because they would not have a color blind child. 5. **Conclusion:** - The only viable option is **Statement 1**: the husband is color blind, and the wife is not (she could be a carrier). ### Final Answer: The true statement about this couple is: **The husband is color blind, and the wife is not.**
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