The Zenkey is a hybrid animal produced from a cross between a species of zebra with a diploid number of 44 and a donkey with a diploid number of 62 - VCE - SSCE Biology - Question 1 - 2005 - Paper 1

Gametes are formed through a process called meiosis. This is a specialized type of cell division that reduces the chromosome number in half, resulting in the production of haploid cells.

During meiosis, the following events occur:

1. Prophase I: Homologous chromosomes pair up and exchange segments (crossing over).
2. Metaphase I: Paired homologous chromosomes align at the cell's equator.
3. Anaphase I: Homologous chromosomes are pulled apart to opposite poles of the cell.
4. Telophase I and Cytokinesis: The cell divides into two haploid daughter cells.
5. Meiosis II: Each haploid cell undergoes a second division (similar to mitosis), resulting in four haploid gametes overall.

Zenkeys are sterile due to chromosomal incompatibility. Because they are hybrids, the different numbers of chromosomes from their zebra and donkey parents (53 total) result in irregular pairing during meiosis. This irregularity prevents the formation of viable gametes, rendering the Zenkey unable to produce offspring.