The buffer is re-used. Set up blot as described below in picture. Always use gloves when handling the nylon membrane. Leave blot overnight. Carefully remove the nylon membrane and incubate in neutralisation solution for 30 minutes.
Air dry the nylon membrane and fix DNA to the filter.
This blot can now be stored either sealed in a plastic bag or saran wrap at room temperature until required. Resist the temptation to put really heavy weights on top of the Southern blot set up. Transfer works by capillary action and excessive weights may result in a squashed gel and diffuse bands on probing. To be able to determine the approximate size of any hybridization signals produced when the Southern blot is subjected to probing, it is necessary to photograph the gel with a ruler alongside the marker lane. Plot the results of the measurements for each marker band.