* Chromosomes and their role: Chromosomes carry genetic information in the form of genes. During sexual reproduction, offspring inherit half of their chromosomes from each parent.
* Mules: Mules are the offspring of a male donkey (62 chromosomes) and a female horse (64 chromosomes). They inherit 31 chromosomes from the donkey and 32 from the horse, resulting in a total of 63 chromosomes. This odd number makes it difficult for chromosomes to pair up properly during meiosis, the process of creating sex cells (sperm and egg). This leads to uneven distribution of genetic material, making the mule's reproductive cells dysfunctional.
* Ligers: Ligers are the offspring of a male lion (38 chromosomes) and a female tiger (38 chromosomes). While both parents have the same number of chromosomes, there are still significant differences in their genes, leading to issues during meiosis. This results in disrupted chromosome pairing and malfunctioning sex cells, leading to sterility.
In simpler terms:
Imagine trying to fit two mismatched puzzle pieces together. Even though they have the same number of pieces, the shapes won't align properly, preventing the puzzle from being completed. In the case of mules and ligers, the chromosomes from different species don't fit together seamlessly, resulting in infertility.