Final answer:
In an animal's gametes, the chromosome number is reduced to n during meiosis, resulting in haploid cells ready for fertilization.
Step-by-step explanation:
In animals, the number of chromosomes within an animal's gametes, which are sperm or egg cells, is reduced to n by the process of meiosis. This reduction occurs because during meiosis, the genome of a diploid cell (2n), which includes two sets of chromosomes, undergoes one round of DNA replication followed by two rounds of cell division. This process results in four haploid daughter cells (n), each containing only one set of chromosomes, which is half the number found in the diploid parent somatic cells. As an example, human somatic cells are diploid with 46 chromosomes (2n = 46), while human gametes are haploid with 23 chromosomes (n = 23). This reduction in chromosome number is essential for sexual reproduction because it ensures that when two gametes fuse during fertilization, the resulting zygote has the appropriate diploid number of chromosomes.