PDS5A and Cornelia de Lange syndrome: The importance of Pds5 dosage is further highlighted by the frequency of cleft palate, which is 33% (20/61) in Pds5A homozygotes and 5% (4/77) in Pds5A heterozygotes, a finding consistent with the idea that reduced dosage of functional cohesin results in the developmental anomalies characteristic of CdLS.