Another application for the magnetic sequencing is using the hairpin end-to-end distance to detect the successive ligation of oligonucleotide. First step of sequencing by ligation is using a primer to extend a DNA fragment. Extension is first attempted with a fragment starting with adenine, which can only be ligated if the next nucleotide on the opposite strand is a thymine. Then fragments starting with cytosine, guanine and thymine are attempted in turn, and the cycle is repeated. The magnetic field is released after each ligation, and then the length of the extended primer is measured. Upon ligation the primer is extended by seven bases, which is resulting in a detectable increase in the hairpin’s end to end distance. RNase cleavage at position 2 is followed by the ligation for the preparation of the next ligation cycle, so that the next ligation is positioned just ahead of the previous one.