Are euchromatic 9q13-q21 duplication variants tandem segmental amplifications of sequence reciprocal to 9q13-q21 deletions?
The sequences involved in both the 9q13-q21 duplication and deletion appear the same, implying reciprocity and suggesting non-allelic homologous recombination as the underlying mechanism. All four known euchromatic variants of chromosome 9 have now been shown to encompass segmental duplications. Importantly, a set of validated FISH probes was defined for the detection and characterisation of this 9q13-q21 amplification in the context of other chromosome 9 variants, allowing apparently benign variants to be distinguished from pathogenic changes.
Because more and more extreme low-birth-weight infants are surviving in western countries and because of the rising numbers of surviving premature infants in emerging nations, we may be on the verge of an ROP epidemic.