Prophase
Encyclopedia
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 chromatid
s, 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. Prometaphase
, the next step of mitosis, will see the nuclear envelope
and nucleolus
dissappear and the chromosomes being captured by the microtubules.
Ancient Greek
Ancient Greek is the stage of the Greek language in the periods spanning the times c. 9th–6th centuries BC, , c. 5th–4th centuries BC , and the c. 3rd century BC – 6th century AD of ancient Greece and the ancient world; being predated in the 2nd millennium BC by Mycenaean Greek...
πρό (before) and φάσις (stage), is a stage of mitosis
Mitosis
Mitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets, in two separate nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two cells containing roughly...
in which the chromatin
Chromatin
Chromatin is the combination of DNA and proteins that make up the contents of the nucleus of a cell. The primary functions of chromatin are; to package DNA into a smaller volume to fit in the cell, to strengthen the DNA to allow mitosis and meiosis and prevent DNA damage, and to control gene...
condenses (it becomes shorter and fatter) into a highly ordered structure called a chromosome
Chromosome
A chromosome is an organized structure of DNA and protein found in cells. It is a single piece of coiled DNA containing many genes, regulatory elements and other nucleotide sequences. Chromosomes also contain DNA-bound proteins, which serve to package the DNA and control its functions.Chromosomes...
in which the chromatin becomes visible. This process, called chromatin condensation, is mediated by the condensin
Condensin
Condensins are large protein complexes that play a central role in chromosome assembly and segregation in eukaryotic cells.- Subunit composition :...
complex. Since the genetic material has been duplicated in an earlier phase of the cell cycle
Cell cycle
The cell cycle, or cell-division cycle, is the series of events that takes place in a cell leading to its division and duplication . In cells without a nucleus , the cell cycle occurs via a process termed binary fission...
, there are two identical copies of each chromosome in the cell. Identical chromosomes, called sister chromatid
Chromatid
A chromatid is one of the two identical copies of DNA making up a duplicated chromosome, which are joined at their centromeres, for the process of cell division . They are called sister chromatids so long as they are joined by the centromeres...
s, are attached to each other at a DNA element present on every chromosome called the centromere
Centromere
A centromere is a region of DNA typically found near the middle of a chromosome where two identical sister chromatids come closest in contact. It is involved in cell division as the point of mitotic spindle attachment...
. During prophase, giemsa staining can be applied to elicit G-banding in chromosomes. Prophase accounts for approximately 3% of the cell cycle
Cell cycle
The cell cycle, or cell-division cycle, is the series of events that takes place in a cell leading to its division and duplication . In cells without a nucleus , the cell cycle occurs via a process termed binary fission...
's duration.
An important organelle in mitosis is the centrosome
Centrosome
In cell biology, the centrosome is an organelle that serves as the main microtubule organizing center of the animal cell as well as a regulator of cell-cycle progression. It was discovered by Edouard Van Beneden in 1883...
, the microtubule organizing center in metazoans. During prophase, the two centrosomes, which replicate independently of mitosis, have their microtubule
Microtubule
Microtubules are a component of the cytoskeleton. These rope-like polymers of tubulin can grow as long as 25 micrometers and are highly dynamic. The outer diameter of microtubule is about 25 nm. Microtubules are important for maintaining cell structure, providing platforms for intracellular...
-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. Prometaphase
Prometaphase
Prometaphase is the phase of mitosis following prophase and preceding metaphase, in eukaryotic somatic cells. In Prometaphase, The nuclear envelope breaks into fragments and disappears. The tiny nucleolus inside the nuclear envolope, also dissolves. Microtubules emerging from the centrosomes at the...
, the next step of mitosis, will see the nuclear envelope
Nuclear envelope
A nuclear envelope is a double lipid bilayer that encloses the genetic material in eukaryotic cells. The nuclear envelope also serves as the physical barrier, separating the contents of the nucleus from the cytosol...
and nucleolus
Nucleolus
The nucleolus is a non-membrane bound structure composed of proteins and nucleic acids found within the nucleus. Ribosomal RNA is transcribed and assembled within the nucleolus...
dissappear and the chromosomes being captured by the microtubules.