Segregation of inverted chromosome 13 in families ascertained through liveborn recombinant offspring

In humans pericentric inversions are rare structural chromosome abnormalities. Reproductive consequences of inversion heterozygosity depend upon many variables such as the chromosomes involved, the location of breakpoints, frequency of crossovers in the inverted segment, functional impairment of the gametes produced, and the viability of unbalanced zygotes that form. Therefore, each pericentric inversion may be studied as a unique mutation. This paper analyzes the segregation of inversion 13 chromosomes resulting from breaks at bands 13p12 and 13q21/22 in 11 apparently unrelated families. Ten of these families were ascertained through malformed fetuses or infants with a recombinant 13 duplication q, deletion p chromosome.