Changes in the pattern of RNA synthesis in mouse limb cartilage during early development

Patterns of RNA synthesis using tritiated uridine were studied in organ cultures of mouse embryonic limb cartilage and epiphyseal cartilage from mice 5 days of age. The cold phenol-sodium dodecyl sulfate extracted RNA was characterized by methylated albumin kieselguhr chromatography and polyacrylamide gel electrophoresis. The general pattern of synthesis indicates the persistence of primarily low molecular weight tRNA and a diminishing synthesis of rRNA in the older cartilage. Data show that the increased radioactivity in the low molecular weight fraction is not due to the accumulation of rRNA breakdown products. These findings are discussed in relation to other age-related studies on RNA biosynthesis.