I've always been fascinated by weird animals. Especially those with out-of-the-ordinary genetics.
Transcaucasian mole vole. Image Courtesy of Heike HimmelreichOne of my favorites is a little burrowing mammal called a Transcaucasian mole vole. These guys live in the Caucasus Mountains of Armenia, Iran, Turkey, and Azerbaijan. There they are born, live, have babies and die. All without a Y chromosome.
This is really bizarre. In most mammals, two X chromosomes usually means that the animal is female and an X and a Y means the animal is male. All mole voles have a single X chromosome. So technically, there shouldn’t be any males running around. And yet, clearly, there are.
So what distinguishes a boy mole vole from a girl mole vole genetically? No one really knows.
In most mammals, the Y chromosome causes a fertilized egg to turn into a male because of the SRY gene. This gene starts a cascade of events that eventually results in a male.