Even by mouse standards, the African pygmy mouse is tiny. It weighs just 5 grams, and is little more than 11 centimetres long, making it one of the smallest mammals. It can reportedly quench its thirst just by licking the morning dew off pebbles that it stacks in front of its burrow. It is a popular pet, although its body is so fragile that owners should not pick it up.
The mouse’s most remarkable feature is hidden within its cells. In the 1960s, geneticists found three sex chromosomes floating in its gene pool, rather than the two most mammals carry. As well as the normal X and Y sex chromosomes, there is a modified X called X*
Read the full, original story: Superfemale mice have secret male DNA
