Practice question

X-linked dominant affected father carries mutant dominant allele on his single X chromosome. During spermatogenesis, he produces X-bearing sperm carrying mutant chromosome and Y-bearing sperm without it. Daughters result exclusively from fertilization by X-bearing sperm, automatically receiving paternal X chromosome with dominant allele, so one hundred percent daughters express trait regardless of maternal contribution, assuming complete penetrance. Sons arise from Y-bearing sperm, obtaining X chromosome only from mother, thus never inheriting paternal X-linked dominant allele. This distinct transmission distinguishes X-linked dominant from autosomal dominant fifty percent.