Challenging conventional wisdom on sex determination: The determination of an organism's sex has long been thought to be solely dependent on the presence or absence of protein-coding genes such as SRY or SOX9. However, researchers have now focused on the hypothesis that even small variations in non-coding DNA, which does not directly code for proteins but regulates gene expression, can lead to a complete reversal of sex.

Research methodology: Utilizing CRISPR-Cas9 for genetic sex conversion, the research team employed the CRISPR-Cas9 gene editing technology to precisely replace specific non-coding sequences in the genome of female mice (XX) with male-like sequences. This approach did not involve adding or removing genes but rather modifying the 'switch' that controls gene function.

Key findings: The formation of fully functional testicular tissue was a surprising outcome. In genetically female mice, complete testicular tissue developed instead of ovaries.