A baboon (Papio hamadryas) with an isochromosome for the long arm of the X.

A 5.5-yr-old female baboon was evaluated for sexual immaturity. She was small for her age and had normal external female genitalia. However, she lacked cyclical perineal turgescence and displayed atypical coloration of the perineal skin. Laparoscopy revealed a small uterus and absence of both ovaries. Cytogenetic analysis revealed a 42,X,i(X)(q10) karyotype. DNA analysis using loci DXS1683, which maps to Xp22.1, and DXS297, which maps to Xq27.3, was consistent with inheritance of the normal X chromosome from the dam and formation of the isochromosome Xq from the paternal X.