A LONGITUDINAL GENETIC-STUDY OF TAIL TENDON FIBER BREAK TIME

Tail tendon fibre break time (TTFBT), an indicator of collagen cross-l inkage, was measured longitudinally in C57BL/6, DBA/2 and B6D2F1 mice, and F2 and backcross genotypes. TTFBT was assessed at 50, 150, 300 an d 450 days of age. The distribution of means of these six genotypes su ggests substantial genetic influence on this phenotype. Broad sense he ritability, as assessed in a classical biometrical analysis, was negli gible at 50 and 150 days, but accounted for between 25 and 43% of the variance at 300 to 450 days. The stability and reliability of TTFBT we re also examined. Reliability was extremely high for each occasion; st ability increased from moderate to substantial levels with increasing age, and may be influenced by heterozygosity.