Extra small marker chromosome associated with normal phenotype due to 3:1 disjunction of t(14;22) in a parent. Implications for the origin of marker chromosomes.

A family with segregation of a translocation t(14;22) (q31;q11) is is reported. The proband was ascertained by chromosome analysis after repeated spontaneous abortions in his wife. His normal sister was found to have the karyotype 47,XX,+ der (22). The small size and banding pattern of chromosome 22 make it difficult to determine the breakpoint with certainty, but it was judged to be at q11. This small marker chromosome could thus be similar to the one found in the cat eye syndrome, and further studies may cast light on gene(s) involved in this syndrome.