A familial variant of chromosome 9.

In 1966 Court Brown et al described a group of heritable human chromosomal variants which ap- peared to lack detectable phenotypic effects. These variant or marker chromsomes appear longer and have altered morphology and arm ratio. Court Brown suggested that the morphological differences generally resulted from changes in length at the secondary constrictions. In his series of 756 sub- jects, approximately 217% showed this type of variation mainly involving members of groups D, E, appeared in varying frequency in the different members of the family and in the different tissues of the proband 202 on August 10,