Question

If a colour blind man marries a carrier woman for colour blindness, chances of their children to become colour blind is

• A. 100%
• B. 75%
• C. 50%
• D. 25%

Hint:

Read the question carefully: - "Chance of {sons} being colorblind" = 50% (1 out of 2 sons). - "Chance of {children} being colorblind" = 50% (2 out of 4 children). In this cross, both values happen to be the same, but they can differ.

Answer 1

The Correct Option is C

The question relates to genetics, specifically the inheritance of color blindness, which is a sex-linked recessive trait. To solve the problem, understanding the genetic basis of color blindness is crucial. 

Color blindness is linked to the X chromosome and is recessive. This means:

• A female has two X chromosomes (XX) and a male has one X and one Y chromosome (XY).
• For color blindness to manifest in males, they need only one affected X chromosome (since the Y chromosome does not carry the gene for color vision).
• For females to be color blind, both of their X chromosomes must carry the gene for color blindness (since it is recessive).

Let's represent:

• X^c - X chromosome with the color blindness gene.
• X - Normal X chromosome (without the gene for color blindness).

Given:

• The man is color blind: XY^c
• The woman is a carrier: X X^c

Now, let's determine the possible genotypes of their children:

Female Gametes	X	Xc
Male Gametes (X)	XX	XXc
Male Gametes (Yc)	XY	XcY

Analyzing the genotypes of the offspring:

• XX - Normal daughter
• XX^c - Carrier daughter (normal vision)
• XY - Normal son
• X^cY - Color blind son

Conclusion: Therefore, out of all children, 50% will be color blind (specifically, the sons), making option 50% the correct answer.