Based on the pedigree chart you provided, the following is the correct placement of the black and white squares:
Black squares:
- Female I-2
- Male II-2
- Male III-2
White squares:
- Male I-1
- Female II-1
- Female II-3
- Male III-1
Dashed boxes:
- Female I-1: Carrier
- Male II-1: Normal
X-linked recessive traits are more common in males than females because males only have one X chromosome. If a male inherits a recessive allele for an X-linked trait on his X chromosome, he will express the trait because he does not have a dominant allele to mask it. Females, on the other hand, have two X chromosomes. If a female inherits a recessive allele for an X-linked trait on one of her X chromosomes, she will only express the trait if she also inherits a recessive allele on her other X chromosome. If she inherits a dominant allele on one of her X chromosomes, she will be a carrier for the trait but will not express it herself.
In the pedigree chart you provided, female I-2 is a carrier for the X-linked recessive trait because she has an affected son (male II-2). Male II-2 expresses the trait because he inherited the recessive allele from his mother and does not have a dominant allele to mask it. Female II-1 is not a carrier for the trait because she has an unaffected son (male III-1). Male III-2 expresses the trait because he inherited the recessive allele from his mother.
Conclusion:- The pedigree chart shows that the X-linked recessive trait is being inherited in a classic X-linked recessive pattern. The trait is more common in males than females, and carrier females can pass the trait on to their sons without expressing it themselves.