ONTOGENIC CHANGES IN GENETIC-REGULATION OF FETAL MORPHOMETRICS IN BABOONS (PAPIO-HAMADRYAS SUBSPP.)

It is known that different genes are expressed during ontogeny; howeve r, it is unclear how variation in that expression is associated with c hanges in growth patterns, The objective of this study is to assess ho w genetic variation in fetal morphology changes with ontogeny in baboo ns. Longitudinal measures of the head and femur (60 to 180 days gestat ion) were available for 892 pregnancies. We used a genetic model that allowed both the genetic and environmental variances (sigma(G)(2) and sigma(E)(2)) to change with age and estimated genetic and environmenta l correlations (rho(G) and rho(E)) between measurements at different a ges. The results indicate a significant increase in the genetic varian ce for biparietal diameter and femur length but not for head circumfer ence and fronto-occipital diameter. The rho(G) estimates for all measu res decreased as the age between measures increased from 0 to 120 days , indicating that different groups of genes are expressed early in ges tation and late in gestation. The rho(E) estimates dropped rapidly fro m 1 to 0 for all measures, indicating temporally localized environment al influences on fetal growth. Thus fetal morphometrics are significan tly heritable and those genes that influence them show age-specific ex pression during ontogeny.