A method of analyzing genetic markers includes binding a set of probes to a segment of single stranded nucleic acids. The segment of single stranded nucleic acids includes a repeat region formed of at least two of a repeat unit. The repeat unit can include at least two nucleic acids. The set of probes includes a first probe complementary to the repeat unit. The method can further include directing the segment through a nanopore device and measuring a signal through the nanopore device. The signal can be indicative of the number of repeat units.