Prophase
Then, at a critical point during interphase (called the S phase), the cell duplicates its chromosomes and ensures its systems are ready for cell division. If all conditions are ideal, the cell is now ready to move into the first phase of mitosis. Figure 1: During prophase, the chromosomes in a cell's nucleus condense to the point that they can be viewed using a light microscope. Prophase is the first phase of mitosis. During this phase, the chromosomes inside the cell's nucleus condense and form tight structures. In fact, the chromosomes become so dense that they appear as curvy, dark lines when viewed under a microscope (Figure 1). The homologous chromosomes pair and exchange DNA to form recombinant chromosomes. Prophase I is divided into five phases: 1  Leptotene: chromosomes start to condense. 2  Zygotene: homologous chromosomes become closely associated (synapsis) to form pairs of chromosomes (bivalents) consisting of four chromatids (tetrads). During interphase, the cell's DNA is not condensed and is loosely distributed. A stain for heterochromatin (which indicates the position of chromosomes) shows this broad distribution of chromatin in a mouse cell (upper left). The same stain also shows the organized, aligned structure of the chromosomes during mitosis. Mitosis. Mitosis is a form of eukaryotic cell division that produces two daughter cells with the same genetic component as the parent cell. Chromosomes replicated during the S phase are divided in such a way as to ensure that each daughter cell receives a copy of every chromosome. During mitosis, a eukaryotic cell undergoes a carefully coordinated nuclear division that results in the formation of two genetically identical daughter cells. Mitosis itself consists of five active steps, or phases: prophase, prometaphase, metaphase, anaphase, and telophase. The DNA is condensed into visible chromosomes in the first phase of mitosis, known as prophase. All cells, whether plant or animal, undergo mitosis in order to make new cells. The cell cycle. Actively dividing eukaryote cells pass through a series of stages known collectively as the cell cycle: two gap phases (G1 and G2); an S (for synthesis) phase, in which the genetic material is duplicated; and an M phase, in which mitosis partitions the genetic material and the cell divides. 1  G1 phase.
http://www.nature.com/scitable/topicpage/Replication-and-Distribution-of-DNA-during-Mitosis-6524841 http://www.nature.com/scitable/topicpage/Replication-and-Distribution-of-DNA-during-Mitosis-6524841 http://www2.le.ac.uk/departments/genetics/vgec/schoolscolleges/topics/cellcycle-mitosis-meiosis http://www.nature.com/scitable/topicpage/chromosomes-14121320 http://www2.le.ac.uk/departments/genetics/vgec/schoolscolleges/topics/cellcycle-mitosis-meiosis http://www.nature.com/scitable/topicpage/Replication-and-Distribution-of-DNA-during-Mitosis-6524841 http://www.ehow.com/info_12049431_dna-condensed-phases.html http://www2.le.ac.uk/departments/genetics/vgec/schoolscolleges/topics/cellcycle-mitosis-meiosis
which phase of mitosis does dna condense into chromosomes