Cytogenetics of Down’s Syndrome (Mongolism) III. Frequency of Interchange Trisomics and Mutation Rate of Chromosome Interchanges

摘要

An attempt is made to obtain an estimate of the frequency of interchange trisomic Down’s syndrome within the general population. This estimate is used to calculate the interchange mutation rate (τ) involving chromosome 21 and resulting in the formation of interchange trisomics. Inadequacies and shortcomings of the data used, the assumptions required and the method employed are discussed. A maximum estimate of 2.71 × 10–5 (1 in 37,000) and a minimum of 2.07 × 10–5 (1 in 48,000) interchanges per chromosome 21, per gamete, per generation, resulting in the formation of interchange trisomics is