Deletions

Deletions of the WBS region occur because of unequal meiotic recombination in grandparental chromosomes (44-46). Approximately two-thirds of these recombinations are interchromosomal rearrangements between chromosome 7 homologs, whereas the remainder are intrachromosomal and involve sister chromatids of the same chromosome 7. A survey of all reported cases where inheritance was determined reveals no bias in inheritance of the

Fig. 3. Genomic rearrangements of the Williams-Beuren syndrome (WBS) region. All documented, recurrent rearrangements of the WBS region are shown. The block components of the flanking low-copy repeats (LCRs) are shown, along with the relative position of ELN, which lies at the center of the commonly deleted region. The regions to which the breakpoints have been localized are indicated by boxes. The WBSinv-2 inversion does not appear to be an LCR-mediated event. The duplication extends beyond the WBS region in both directions.

Fig. 3. Genomic rearrangements of the Williams-Beuren syndrome (WBS) region. All documented, recurrent rearrangements of the WBS region are shown. The block components of the flanking low-copy repeats (LCRs) are shown, along with the relative position of ELN, which lies at the center of the commonly deleted region. The regions to which the breakpoints have been localized are indicated by boxes. The WBSinv-2 inversion does not appear to be an LCR-mediated event. The duplication extends beyond the WBS region in both directions.

deletion, as it apparently occurs with equal frequency on maternally or paternally inherited chromosomes (47-49).

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