The inheritance of factors associated with joint mobility.
From a sample of 1,500 individuals belonging to 442 migrant nuclear families from northeastern Brazil, information on the interphalangial mobility was obtained: (a) the grades of extension of both the right and left thumbs and (b) the angle (in degrees) formed by the distant and proximal phalanx of the thumb. The first principal component of these variables was estimated and called "extensibility." A negative association of extensibility and age, as well as with inbreeding, was detected. Complex segregation analysis was applied to extensibility and both a multigenic mechanism and an extra transmissible component were detected. Mendelian inheritance was rejected, while a model with multifactorial inheritance, together with a factor that is inherited with a transmission probability different from 1/2 (tau = 0.63), was not rejected. These findings were supported by path analysis, which showed an important biologic inheritance (h2 = 0.675) and the existence of a small but significant cultural component (c2 = 0.003). The observed "inbreeding" effect, therefore, could not be attributed to a genetic mechanism and probably is the effect of concomitant environmental variability.
Departamento de Genética, Instituto Oswaldo Cruz-FIOCRUZ, Rio de Janeiro, Brasil.
M M
MM
Moura
M F
MF
Feitosa
J
J
Laredo Filho
H
H
Krieger
D001938:Brazil / Q000453:epidemiology; D005260:Female; D030342:Genetic Diseases, Inborn / Q000453:epidemiology / Q000235:genetics*; D005838:Genotype; D006225:Hand; D006801:Humans; D007596:Joints / Q000503:physiopathology*; D008297:Male