Women born with a rare condition that gives them a Y chromosome do not only look like women physically, they also have the same brain responses to visual sexual stimuli, says a new study. And the condition is known as complete androgen insensitivity or CAIS.
Females normally have an XX chromosome pair and males have an XY chromosome pair. The Y chromosome was identified as the sex-determining chromosome in 1905.
In an individual with CAIS, the body's cells are unable to respond to androgen, or male hormones.
"Our findings clearly rule out a direct effect of the Y chromosome in producing masculine patterns of response," said Kim Wallen, professor of psychology and behavioural neuro-endocrinology at Emory University in the US.
"It is further evidence that we need to revamp our thinking about what we mean by 'man' and 'woman'," Wallen added.
The study involved 13 women with CAIS in addition to women without CAIS and men.
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The researchers used functional magnetic resonance imaging (fMRI) to study the neural activity their brains.
"We did not find any difference between the neural responses of women with CAIS and typical women, although they were both very different from those of the men in the study," said co-researcher Stephan Hamann.
"It further confirms that women with CAIS are typical women psychologically, as well as their physical phenotype, despite having a Y chromosome," Hamann concluded.
The study appeared in the journal Hormones and Behavior.