New evidence of unbalanced sex-chromosome constitutions in the mouse

Some anomalous results are described of genetical tests using the sex-linked markers Tabby and Bent-tail . The results are shown to be consistent with the demonstration by Welshons & Russell (1959) that the X/O chromosome constitution is female, and suggest that the condition can arise from non-disjunction in the female as well as from non-disjunction in the male parent. A single animal of presumed X/X/y constitution appeared anatomically to be fully male, but died before breeding test could be performed.