You have been asked to perform prenatal testing for a couple where the father has an AD disorder apparent within the first six months of life. The couple has one child who is currently 3 years old and unaffected. Although the gene has been localized, it has not yet been identified so direct testing is not possible. You have a linked marker (a dinucleotide repeat) that is approximately 10 cM from the gene. The father has alleles of 125 and 129 bp. The mother and the unaffected child are homozygous for the 125 bp allele. The fetus has 125 and 129 bp alleles. The chance the fetus is affected is closest to
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