Final answer:
A pair of homologous chromosomes consists of two sets of sister chromatids that have synapsed, and each chromosome has replicated to form two identical sister chromatids joined at the centromere.
Step-by-step explanation:
A pair of homologous chromosomes includes two sets of sister chromatids that have synapsed. During the interphase period of the cell cycle, particularly in the S phase for DNA synthesis, the amount of DNA within a cell is doubled. This results in each chromosome being replicated to form two identical copies known as sister chromatids, joined together at a region called a centromere, resulting in the familiar "X" shape as depicted Later, during metaphase I of meiosis, these chromosomes will exhibit tight pairing termed synapsis, which allows for the precise alignment of genes and the potential for crossover events between non-sister chromatids.