Question

drag the given black and white squares to the correct location on the chart. each square can be used more than once.
the pedigree chart shows the inheritance of an x - linked recessive genetic trait. fill in the dashed boxes to correctly complete the chart.

Explanation:

Step1: Identify parental genotypes

Father (unaffected male): $X^NY$; Mother (affected female): $X^aX^a$

Step2: Find their son's genotype

Son gets $Y$ from father, $X^a$ from mother: $X^aY$ (affected male, black square)

Step3: Analyze left couple's offspring

Unaffected female ($X^NX^N$) × affected male ($X^aY$): Daughters get $X^N$ from mother, $X^a$ from father (carriers, already filled). Son gets $X^N$ from mother, $Y$ from father: $X^NY$ (unaffected male, white square)

Step4: Analyze right couple's father

Carrier female ($X^NX^a$) has affected son ($X^aY$): Son gets $Y$ from father, so father is $X^NY$ (unaffected male, white square)

Answer:

1. First dashed square (son of top couple): Black square (affected male)
2. Second dashed square (father of left offspring): Black square (affected male)
3. Third dashed square (son of left couple): White square (unaffected male)
4. Fourth dashed square (father of right offspring): White square (unaffected male)