The effect of structural aberrations of the chromosomes on reproductive fitness in man. II. Results.

: Reproductive fitness was measured in the following seven classes of pedigrees: (1) D/D Robertsonian translocations ascertained through a euploid proband; (2) D/G Robertsonian translocations ascertained through a euploid proband: (3) reciprocal translocations ascertained through a euploid proband; (4) inversions ascertained through a euploid proband; (5) all translocations and inversions ascertained through an aneuploid proband; (6) those ascertained through a proband with a ring, marker, or supernumerary chromosome; (7) those ascertained through a proband with an extreme variant chromosome. For each group reproductive fitness was calculated in two ways. One method was based on live births, fetal and infant deaths and generation time of those individuals carrying a chromosome abnormality or variant by comparison with their first degree relatives who were known to have a normal chromosome constitution. The second method was based on the proportion of sporadic cases obtained from segregation analysis. The results obtained using both methods are presented and discussed.