Before a cell can divide, it must produce a new copy of each of its chromosomes, and it does this during a specific part of interphase called the DNA-synthesis phase, or S phase, of the cell-division cycle; the part of interphase preceding S phase is called Gap 1, or G1, and the part following S phase is called Gap 2, or G2. In a typical higher eucaryotic cell the S phase lasts for about 8 hours. By its end each chromosome has been replicated to produce two complete copies, which remain joined together at their centromeres until the M phase that soon follows. Chromosome duplication requires both the replication of the long DNA molecule in each chromosome and the assembly of a new set of chromosomal proteins onto the DNA to form chromatin.
(copied chromosome)
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A replicated chromosome is a chromosome that has been copied during the S phase of the cell cycle, resulting in two identical sister chromatids joined at the centromere. This duplication ensures that each daughter cell receives a complete set of genetic material during cell division.
In late anaphase and G1 of interphase, a chromosome is unreplicated and consists of a single DNA double helix. A replicated chromosome contains two identical DNA double helices.
Interphase is when DNA replication occurs. :)
A replicated chromosome consists of an exact copy (assuming no mutations) of the original chromosome, which is composed of DNA and proteins called histones.
DNA and Protein
Chromosome replication occurs before both mitosis and meiosis. During the S phase of the cell cycle, DNA is replicated in preparation for cell division. In mitosis, replicated chromosomes are separated into two identical daughter cells, while in meiosis, replicated chromosomes are separated twice to produce haploid gametes.