A rapid procedure for extracting genomic DNA from leukocytes.

1. Collect 5 ml of blood in a vacutainer tube (Becton Dickinson) containing EDTA and mix. 2. Make volume up to 10 ml with solution 1 (10 mM Tris pH 7.6; 10 mM KC1; 10 mM MgCy. 3. Add 120 /il Nonidet P40 (BDH) to lyse the cells. Mix well by inverting several times. 4. Spin down the nuclear pellet at 2000 rpm for 10 mins. 5. Pour off the supernatant without dislodging the pellet. The pellets can be stored frozen. 6. Gently resuspend pellet well in 800 /il of solution 2 (10 mM Tris pH 7.6; 10 mM KC1; 10 mM MgCl2; 0.5 M NaCl; 0.5% SDS; 2 mM EDTA). Solution 2 will lyse the nuclei so be careful not to shear the DNA. Transfer to a 1.5 ml microcentrifuge tube. 7. Add 400 /il of distilled phenol (saturated with 1 M Tris pH 8.0) and mix well. 8. Microfuge for 1 min at 12000 rpm. Transfer upper phase to a clean microfuge tube. Do not worry about transferring a little of the interface. 9. Add 200 /tl of phenol and 200 /il of chloroform :isoamyl alcohol (24:1). Mix well by inverting. 10. Spin for 1 min at 12000 rpm. Transfer upper phase to a clean microfuge tube. 11. Add 700 /tl of chloroform:isoamyl alcohol and extract as above. 12. Transfer upper aqueous phase to a small clean container. Avoid removing the interface. Add 2 volumes of ice cold ethanol and mix to precipitate the DNA*. 13. With the sealed tip of a pasture pipette, transfer the DNA fibres to a microcentrifuge tube containing 1 ml of 70% ethanol. Mix well to wash the DNA. 14. Spin for 5 mins at full speed. Discard the ethanol and dry pellet in a speed vac. Resuspend DNA in sterile water at 65°C. Do not over-dry genomic DNA or it will be difficult to resuspend. SIZE A / /Kb Hindll l