Anaphase, is from the
ancient GreekAncient Greek is the historical stage in the development of the Greek language spanning across the Archaic , Classical , and Hellenistic periods of ancient Greece and the ancient world. It is predated in the 2nd millennium BC by Mycenaean Greek...
ἀνά (up) and
φάσις (stage), is the stage of
mitosisMitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets in two daughter nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two daughter cells containing...
when
chromosomeA chromosome is an organized structure of DNA and protein that is 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...
s separate in a
eukaryoticA eukaryote is an organism whose cells contain complex structures enclosed within membranes. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear envelope, within which the genetic material is carried...
cellThe cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of an organism that is classified as living, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos...
. Each
chromatidA chromatid is one among the two identical copies of DNA making up a replicated chromosome, which are joined at their centromeres, for the process of cell division . The term is used so long as the centromeres remain in contact...
moves to opposite poles of the cell, the opposite ends of the
mitotic spindleIn cell biology, the spindle apparatus is the structure that separates the chromosomes into the daughter cells during cell division. It is part of the cytoskeleton in eukaryotic cells...
, near the
microtubule organizing centerThe microtubule-organizing center is a structure found in eukaryotic cells from which microtubules emerge. MTOCs have two main functions: The organization of eukaryotic flagella and cilia and the organization of the mitotic and meiotic spindle apparatus separating the chromosomes during cell...
s. During this stage,
anaphase lagAnaphase lag describes the delayed movement during anaphase of one homologous chromosome in mitosis or of one chromatid in meiosis. The result is that the lagging chromosome is not incorporated into the nucleus of one of the daughter cells and there will be one normal cell and one cell with...
could happen.
Anaphase begins abruptly with the regulated triggering of the metaphase-to-anaphase transition and accounts for approximately 1% of the cell cycle.
Anaphase, is from the
ancient GreekAncient Greek is the historical stage in the development of the Greek language spanning across the Archaic , Classical , and Hellenistic periods of ancient Greece and the ancient world. It is predated in the 2nd millennium BC by Mycenaean Greek...
ἀνά (up) and
φάσις (stage), is the stage of
mitosisMitosis is the process by which a eukaryotic cell separates the chromosomes in its cell nucleus into two identical sets in two daughter nuclei. It is generally followed immediately by cytokinesis, which divides the nuclei, cytoplasm, organelles and cell membrane into two daughter cells containing...
when
chromosomeA chromosome is an organized structure of DNA and protein that is 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...
s separate in a
eukaryoticA eukaryote is an organism whose cells contain complex structures enclosed within membranes. The defining membrane-bound structure that sets eukaryotic cells apart from prokaryotic cells is the nucleus, or nuclear envelope, within which the genetic material is carried...
cellThe cell is the basic structural and functional unit of all known living organisms. It is the smallest unit of an organism that is classified as living, and is often called the building block of life. The Alberts text discusses how the "cellular building blocks" move to shape developing embryos...
. Each
chromatidA chromatid is one among the two identical copies of DNA making up a replicated chromosome, which are joined at their centromeres, for the process of cell division . The term is used so long as the centromeres remain in contact...
moves to opposite poles of the cell, the opposite ends of the
mitotic spindleIn cell biology, the spindle apparatus is the structure that separates the chromosomes into the daughter cells during cell division. It is part of the cytoskeleton in eukaryotic cells...
, near the
microtubule organizing centerThe microtubule-organizing center is a structure found in eukaryotic cells from which microtubules emerge. MTOCs have two main functions: The organization of eukaryotic flagella and cilia and the organization of the mitotic and meiotic spindle apparatus separating the chromosomes during cell...
s. During this stage,
anaphase lagAnaphase lag describes the delayed movement during anaphase of one homologous chromosome in mitosis or of one chromatid in meiosis. The result is that the lagging chromosome is not incorporated into the nucleus of one of the daughter cells and there will be one normal cell and one cell with...
could happen.
Anaphase begins abruptly with the regulated triggering of the metaphase-to-anaphase transition and accounts for approximately 1% of the cell cycle. At this point the Anaphase becomes activated. This terminate activity by
cleavingCleave could refer to:*Cleave, an Austrian alternative rock band.*Cleave, a Japanese hardcore punk band.*Cleave, , to adhere or to split.*Thomas L. Cleave, a surgeon captain...
and inactivating the M-phase cyclin required for the function of M-phase cyclin dependent kinases (M-Cdks). It also cleaves
securinSecurin is a protein involved in anaphase triggering. It has two identified roles; the first one is to help the transport of separase to the nucleus and the second role is to inhibit the catalytic activity of separase. Securin is ubiquitinated by the Anaphase Promoting Complex , and then degraded...
, a protein that inhibits the
proteaseA protease breaks down proteins. A protease is any enzyme that conducts proteolysis, that is, begins protein catabolism by hydrolysis of the peptide bonds that link amino acids together in the polypeptide chain forming the protein...
known as
separaseSeparase is a cysteine protease responsible for triggering anaphase by hydrolysing cohesin which is the protein responsible for binding sister chromatids during metaphase....
. Separase then cleaves
cohesinCohesin is the protein complex responsible for binding the sister chromatids during synthesis through the G2 phase and into mitosis phase. When two sister chromatids are bound along their lengths by cohesin, the attachment is referred to as sister chromatid cohesion...
, a protein responsible for holding sister chromatids together.
During
early anaphase (or Anaphase A) the chromatids abruptly separate and move towards the spindle poles. This is achieved by shortening of the spindle microtubules, and forces are mainly exerted at the kinetochores.
- When the chromatids are fully separated late anaphase (or Anaphase B) begins. This involves the polar microtubules elongating and sliding relative to each other to drive the spindle poles further apart. Anaphase B drives separation of the sister centrosomes to their opposite poles through three forces. Kinesin proteins attached to polar microtubules push the microtubules past one another. A second force involves pulling of the microtubules by cortex-associated cytosolic dynein. The third force for the separation of chromosomes involves lengthening the polar microtubules at the plus end.
These two processes were originally distinguished by their different sensitivities to drugs, and they are mechanically distinct.
- Early anaphase (anaphase A) involves shortening kinetochore microtubules by depolymerization at the plus end. During this, a sliding collar allows the movement of the chromatids. No motor protein is involved since and ATP-depletion does not inhibit the early anaphase.
- Late anaphase (anaphase B) involves both the elongation of overlap microtubules and the use of two distinct sets of motor proteins: one of these pulls overlap microtubules past each other, the other pulls on astral microtubules that have attached to the cell cortex.
The contributions of early anaphase and late anaphase to anaphase as a whole vary with cell type. In mammalian cells, late anaphase follows shortly after early anaphase and extends the spindle to around twice its
metaphaseMetaphase, from the ancient Greek μετά and φάσις , is a stage of mitosis in the eukaryotic cell cycle in which condensed & highly coiled chromosomes, carrying genetic information, align in the middle of the cell before being separated into each of the two daughter cells...
length; in contrast
yeastYeasts are eukaryotic micro-organisms classified in the kingdom Fungi, with about 1,500 species currently described; they dominate fungal diversity in the oceans. Most reproduce asexually by budding, although a few do so by binary fission...
and certain
protozoaProtozoa or Cornelius protozoans Protozoa or Cornelius protozoans Protozoa or Cornelius protozoans (from Greek πρῶτον proton "first" and ζῷα zoa "animals"; singular protozoon; (the word "protozoan" is originally an adjective, used as a noun) are microorganisms classified as unicellular eukaryotes....
use late metaphase as the main means of chromosome separation and can extend the spindle to up to 15 times its metaphase length in the process.