XY female marmoset (Callithrix jacchus).

A marmoset (Callithrix jacchus) with atypical external genitalia was phenotypically and genetically characterized. Testosterone concentration correlated with that of female marmosets. Externally, there was only one opening for the urethra. Internal genitalia were characteristic of those of female marmosets, and consisted of ovaries, with follicles in various developmental stages, and uterus. Microscopically, a normal vaginal structure was found. An XX/XY chimerism and high steroid hormone values are normally found in common marmosets. Genetic analysis was used for in vivo determination of sex. The Y-linked zinc finger protein gene (ZFY) last intron, and sex-determining region Y gene (SRY) exon were found by use of polymerase chain reaction and posterior sequencing analyses, indicating that this marmoset had Y-linked chromosome sequences. Normal SRY exons can, therefore, be associated with female internal sexual organs in marmosets; this may be the first XY female described in non-human primates.