[Answer] Spindle fibers attach to kinetochores during _____.

Answer: prometaphase
Spindle fibers attach to kinetochores during _____.
A kinetochore is a disc-shaped protein structure associated with duplicated chromatids in eukaryotic cells where the spindle fibers attach during cell division to pull sister chromatids apart. The kinetochore assembles on the centromere and links the chromosome to microtubule polymers from the mitotic spindle during mitosis and meiosis. Its proteins also help to hold the sister chromatids together and pla…
A kinetochore is a disc-shaped protein structure associated with duplicated chromatids in eukaryotic cells where the spindle fibers attach during cell division to pull sister chromatids apart. The kinetochore assembles on the centromere and links the chromosome to microtubule polymers from the mitotic spindle during mitosis and meiosis. Its proteins also help to hold the sister chromatids together and play a role in chromosome editing. Details of the specific areas of origin are unknown. Monocentric organisms including vertebrates fungi and most plants have a single centromeric region on each chromosome which assembles a single localized kinetochore. Holocentric organisms such as nematodes and some plants assemble a kinetochore along the entire length of a chromosome. Kinetochores start control and supervise the striking movements of chromosomes during cell division. During mitosis which occurs after chromosomes are duplicated in S phase two sister chromatids are held together by a centromere. Each chromatid has its own kinetochore which face in opposite directions and attach to opposite poles of the mitotic spindle apparatus. Following the transition from metaphase to anaphase the sister chromatids separate from each other and the individual kinetochores on each chromatid drive their movement to the spindle poles that will define the two new daughter cells. The kinetochore is therefore essential for the chromosome segregation that is classically associated with mitosis and meiosis.
The kinetochore contains two regions: • an inner kinetochore which is tightly associated with the centromere DNA and assembled in a specialized form of chromatin that persists throughout the cell cycle ; • an outer kinetochore which interacts with microtubules ; the outer ki…
The kinetochore contains two regions: • an inner kinetochore which is tightly associated with the centromere DNA and assembled in a specialized form of chromatin that persists throughout the cell cycle ; • an outer kinetochore which interacts with microtubules ; the outer kinetochore is a very dynamic structure with many identical components which are assembled and functional only during cell division. Even the simplest kinetochores consist of more than 19 different proteins. Many of these proteins are conserved between eukaryotic species including a specialized histone H3 variant (called CENP-A or CenH3) which helps the kinetochore associate with DNA. Other proteins in the kinetochore adhere it to the microtubules (MTs) of the mitotic spindle . There are also motor proteins including both dynein and kinesin which generate forces that move chromosomes during mitosis. Other proteins such as Mad2 monitor the microtubule attachment as well as the tension between sister kinetochores and activate the spindle checkpoint to arrest the cell cycle when either of these is absent. The actual set of genes essential for kinetochore function varies from one species to another. Kinetochore functions include anchoring of chromosomes to MTs in the spindle verification of anchoring activation of the spindle checkpoint and participation in the generation of force to propel chromosome movement during cell division. On the other hand microtubules are metastable polymers made of α- and β- tubulin alternating between…

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