Instability of Short Arm of Acrocentric Chromosomes: Lesson from Non-Acrocentric Satellited Chromosomes. Report of 24 Unrelated Cases.

Satellited non-acrocentric autosomal chromosomes (ps-qs-chromosomes) are the result of an interchange between sub- or telomeric regions of autosomes and the p arm of acrocentrics. The sequence homology at the rearrangement breakpoints appears to be, among others, the most frequent mechanism generating these variant chromosomes. The unbalanced carriers of this type of translocation may or may not display phenotypic abnormalities.

Prenatal detection by subtelomeric FISH and MLPA of unbalanced meiotic recombinants resulting from parental pericentric inversions.

Objective: Pericentric inversion carriers are predisposed to produce unbalanced gametes that result in conceptuses having either a partial trisomy for one distal segment and a partial monosomy for the other or vice versa. Larger inversions result in smaller unbalanced distal segments and a higher likelihood of a viable fetus. In these cases the structure of the recombinant chromosome is similar to the original balanced inverted or normal ones despite the (unbalanced) genetic content.