Allele specific oligonucleotides (aso) can be used to determine the different alleles present in a dna sample. Single sperm, which have completed meiosis, can be used for a polymerase chain reaction (pcr). The amplified dna is then spotted to filters and hybridized with probes that recognize single nucleotide differences. A sperm sample was collected from a single individual and dna was extracted from individual sperm. For each dna sample, four different regions of the genome were amplified using pcr (called a, b, d, and e). For each dna sample, aso probes were used to determine the allele present (either allele 1 or 2) for each region of the genome amplified. X indicates the allele is present and - indicates the allele is not present.