Telomere length in separated granulocyte and mononuclear cell fractions. Southern blot of Rsa I-digested genomic DNA extracted from density gradient separated peripheral blood granulocytes or mononuclear (MN) cells, probed with (TTAGGG)₄, showing equivalent results for both cell fractions_. Positions of molecular weight markers are shown on the left. Tracks 1 and 2: MN (1) and granulocytes (2) from normal donor age 45 years; tracks 3 and 4: MN (3) and granulocytes (4) from normal donor age 54 years; tracks 5 and 6: MN (5) and granulocytes (6) from normal donor age 57 years.