Question

in females as well. it occurs when abnormal red and green photopigments in the eye are inherited from parents. it causes the person to not be able to distinguish between certain colors with red and green in them. the following pedigree shows a family in which some individuals are affected by colorblindness. family members 6 & 7 in generation ii are expecting a child. the fathers genotype is x^by. the mothers genotype is x^bx^b. use the pedigree and provided punnet square to answer the following question: which of the following describes the possibility of this son being colorblind? a twenty - five percent, because in the punnett square, only one box out of four shows an affected male b fifty percent, because only one of the two males in the punnett square has the genotype for being affected c one hundred percent, because the mother will pass the colorblindness trait to all offspring through her x chromosome d zero percent, because the father is not colorblind

Explanation:

Step1: Analyze the Punnett square

The Punnett square for \(X^{B}Y\times X^{B}X^{b}\) gives the following genotypes: \(X^{B}X^{B}\), \(X^{B}X^{b}\), \(X^{B}Y\), \(X^{b}Y\).

Step2: Count the male genotypes

Among the four genotypes, the male genotypes are \(X^{B}Y\) (unaffected) and \(X^{b}Y\) (affected).

Step3: Calculate the probability

There are 2 male genotypes in total, and 1 of them (\(X^{b}Y\)) is affected. So the probability for a son to be color - blind is \(\frac{1}{2}=50\%\).

Answer:

B. Fifty percent, because only one of the two males in the Punnett square has the genotype for being affected.