Biology

Key Observations:

The disorder is X-linked recessive, meaning a male only needs one recessive X allele () to be affected.
Females need two recessive X alleles () to be affected.
The mother (I-2) is a carrier () because she has an affected son (II-2) and is herself unaffected.
The father (I-1) is unaffected, so his genotype must be .

Analyzing the offspring:

II-1 (normal female): She must have inherited one from her father (I-1) and one