Meiotic analysis of a pericentric inversion, inv(7) (p22q32), in the father of a child with a duplication-deletion of chromosome 7.
In a family in which a large pericentric inversion of chromosome 7 is segregating, two of the four progeny of inversion heterozygotes show severe psychomotor retardation and have the karyotype 46,XX,rec(7),dup q,inv(7)(p22q32), derived from crossing-over within the inversion. Meiotic analysis in one of the heterozygotes revealed no evidence of inversion loops in well-spread pachytene cells. In approximately 20% of cells in diakinesis, the presumptive bivalent 7 had only one chiasma. Two alternatives to the reversed loop mode of meiotic pairing of inversions are proposed. Review of the literature supports the view that "small" pericentric inversions have a much better genetic prognosis than "large" pericentric inversions.
D000015:Abnormalities, Multiple / Q000235:genetics*; D000328:Adult; D002675:Child, Preschool; D002869:Chromosome Aberrations; D002872:Chromosome Deletion; D007446:Chromosome Inversion; D002906:Chromosomes, Human, 6-12 and X; D003434:Crossing Over, Genetic; D005260:Female; D006801:Humans; D008607:Intellectual Disability / Q000235:genetics; D008540:Meiosis; D008938:Mitosis; D010375:Pedigree; D010641:Phenotype; D011596:Psychomotor Disorders / Q000235:genetics