According to an interesting study published in the March 10 edition of the journal Nature, researchers have found that chickens “do not follow the mammalian model” of sex-determining chromosomes; and, as such, some of them may show gender-confusing traits – being half male and half female.

Going by the findings of the researchers at the University of Edinburgh, Scotland, the sex of chicken is not determined by hormones – as it is in the mammals -; rather their sex-determination is based on the fundamental property of the cells themselves.

The oddity in the sex-determination of the chickens came to fore after the biologists’ investigations of several half-male, half-female chickens, called the gynandromorphs. For their study, the researchers relocated male cells into a female embryo, and vice versa; and found that, in both the cases, the cells continued to express their sex-specific hormones.

Noting that the gynandromorphs have a chromosomal malfunction, lead researcher Michael Clinton said that “the major factors determining sexual development are built into male and female cells and derive from basic differences in how sex chromosome genes are expressed.”

In a supplementary perspective article in the same edition of Nature, Lindsey Barske and Blanche Capel of Duke University Medical Center note that the new study clearly reveals that “in birds, sex determination occurs in cells across the entire body, not just in the gonads.”