Unequal crossover in creation of Williams–Beuren syndrome

(a) Normal chromosome 7 structure Centromere I Homologous { copies PMS A and i PMSB with 17 fl igenes between Flanking Ifi—l Flanking ‘thehcopies marker 17 genes marker (b) Homologous chromosome misalignment and unequal crossover DNA loop Homologs misalign, and a copy of PMS on each chromosome loops out. Unequal crossover occurs. Labels 1, 2, 3, and 4 are flanking markers for reference. (c) Deletion and duplication recombinant chromosomes The3 recombinants are.. PMS /PM$ — M A partial deletion chromosome Hybrid gene with a hybrid gene that IS WBS syndrome missing the 17 genes between PMS duplicates... PMS 4 l HybrId gene 1 No phenotypic abnormalities 17 genes 17 genes .and a partial duplication chromosome with PMSA, PMS, a hybrid gene, and duplication of the 17 genes.