Scientists made mice with Y chromosomes female by deleting just 6 tiny molecules

Illustration of the X chromosome floating next to a Y chromosome. Both are depicted in green and yellow.

Mammals' chromosomes have a huge influence over whether an individual develops as male or female — but a new study reveals that the pull of these sex chromosomes can be overridden by tiny molecules called microRNAs. 

The study, published May 7 in the journal Nature Communications, showed that deleting the genes behind specific microRNAs could transform male mice into females in the womb, sparking a complete sex reversal.