Prophase

Prophase, from the ancient Greek πρό (before) and φάσις (stage), is a stage of mitosis in which the chromatin condenses (it becomes shorter and fatter) into a highly ordered structure called a chromosome in which the chromatin becomes visible. This process, called chromatin condensation, is mediated by the condensin complex. Since the genetic material has been duplicated in an earlier phase of the cell cycle, there are two identical copies of each chromosome in the cell. Identical chromosomes, called sister chromatids, are attached to each other at a DNA element present on every chromosome called the centromere. During prophase, giemsa staining can be applied to elicit G-banding in chromosomes. Prophase accounts for approximately 3% of the cell cycle's duration.

An important organelle in mitosis is the centrosome, the microtubule organizing center in metazoans. During prophase, the two centrosomes, which replicate independently of mitosis, have their microtubule-activity increased due to the recruitment of γ-tubulin. The centrosomes will be pushed apart to opposite ends of the cell nucleus by the action of molecular motors acting on the microtubules. The nuclear envelope breaks down to allow the microtubules to reach the kinetochores on the chromosomes, marking the end of prophase. Prometaphase, the next step of mitosis, will see the chromosome being captured by the microtubules.

| chapter = Section 1. The Biology of the Plant Cell – 3. The Plant Cell and the Cell Cycle | pages = 58–67 | isbn = 978-0-7167-1007-3 | oclc = 56051064 | id = LCCN 2004-053303 | url = http://books.google.com/?id=8tz2aB1-jb4C&pg=PA58

| year = 2005 }}</ref>

References

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External links

• Prophase at Online Biology Dictionary