Final answer:
Mules have a haploid number of chromosomes, which leads to hybrid sterility.
Step-by-step explanation:
Mules give rise to a haploid number of chromosomes, which is the reason for hybrid sterility.
Mules are the result of crossing a male donkey (which has 31 chromosomes) with a female horse (which has 32 chromosomes). The resulting mule ends up with 63 chromosomes, which is an odd number for chromosomes.
Since mules have an odd number of chromosomes, they cannot produce balanced gametes for reproduction. This renders them infertile and unable to produce offspring, a condition known as hybrid sterility.