Final answer:
After interphase, each of the original chromosomes is replicated into two sister chromatids, but the total number of chromosomes remains the same; the number of chromatids doubles.
Step-by-step explanation:
During interphase, each chromosome replicates and forms two sister chromatids. These sister chromatids are physically bound together at the centromere. So, after interphase, each chromosome has two chromatids. Since a human cell has 46 chromosomes, the total number of chromatids will be 92 (46 x 2).
Before interphase, each chromosome comprises one chromatid. During the synthesis phase (S phase) of interphase, each chromosome is replicated to consist of two sister chromatids, held together at a region called the centromere. Thus, after interphase, but before cell division, the chromosome count itself does not change; however, because each chromosome has been replicated, the number of chromatids doubles. For example, a human cell which originally has 46 chromosomes will still have 46 chromosomes after replication, but with 92 chromatids in total (46 chromosomes each with 2 chromatids).