Why a mule is sterile and cannot produce gametes by meiosis?

Mules are sterile because they are hybrids resulting from the mating of a male donkey and a female horse, which have different numbers of chromosomes: horses have 64 chromosomes while donkeys have 62. This results in mules having 63 chromosomes, an odd number, which disrupts the pairing of homologous chromosomes during meiOSis. As a result, mules cannot produce viable gametes, making them incapable of reproduction.