While it’s long been known that this blind spot exists in the scientific world, the actual impact on results has been less clear. The new study aims to quantify the differences between male and female study subjects, known as sexual dimorphism. The team analyzed up to 234 physical characteristics in more than 60,000 mice—14,250 wildtype animals, or animals as they typically occur in nature, and 40,192 mutant mice from 2,186 single gene knockout lines. Knockout mice have been genetically engineered, with researchers making a single gene inactive to show what role it plays. The 40,192 mice had a total of 2,186 genes knocked out (though no more than one single gene was knocked out per mouse).