Spindle Fibre
What is the Spindle Apparatus - Spindle apparatus also called spindle fiber is the structure that's separate the chromosomes into daughter cells during cell division. Depending upon the type of cell division , it is also referred to as mitotic spindle during mitosis and meiotic spindle during meiosis.
Shape and Formation - The cellular spindle apparatus includes the spindle microtubules, associated proteins, and any aster present at the spindle poles. The spindle apparatus is vaguely ellipsoid in shape and tapers at the end but spread out in the middle portion also known as midzone. At the pointed ends, known as spindle poles, microtubules are nucleated by the centrosome or aster in most of the animals cells.
Assembly, Chromosome Attachment, and Function During Cell Divison - During spindle assembly in prometaphase, certain spindle microtubules attach to kinetochores, which form on the centromere region of each chromosome. Once the kinetochore captures the spindle fiber, the chromosomes are guided toward the spindle’s midzone, arranging themselves into the metaphase plate.
The center of the spindle determines the plane along which the cell will divide during cytokinesis, ensuring that each daughter cell receives one copy of every chromatid.
Spindle fiber formation is considered complete in metaphase when:
-
Chromosomes are perfectly aligned on the metaphase plate.
-
Non-kinetochore microtubules from opposite poles overlap.
-
Aster microtubules make contact with the plasma membrane.
Once all the chromosomes are aligned with the sister chromatid pointing the opposite ends of the spindle , the cell enter anaphase when protein holding the sister chromatid together is inactivated. This allow the chromatid to separate into full-fledged chromosomes that start moving toward their respective poles. This movement is mediated by the motor proteins along the kinetochores that walk the chromosomes along the microtubules toward the nearest poles.
Similarly, motor proteins attach to non-kinetochores microtubules and walk them away from each other, thus elongating the spindle and pushing apart the spindle poles.
Regulation Of Spindle Assembly - The mitotic kinase Aurora-A is required for proper spindle assembly and separation. LAmbin -B is a key component of spindle matrix helping microtubules assembly and the mitotic spindle will not form without it.
Polo-like kinase, also known as PLK especially PLK1 has important role in spindle maintenance by regulating microtubulin dynamics.
| Topic | Link |
|---|---|
| Biodiversity: Key Facts You Must Know | Read More |
| 30 Best Presentation Topics In Biology In USA | Read More |
| साइकॉन केनाल तंत्र का वर्णन | Read More |
| Difference between Prokaryotic & Eukaryotic cells | Read More |
| Kingdom Fungi - Habitat, Features, Reproduction | Read More |
| 20 Top Wildlife Sanctuaries in India | Read More |
bhaiii absence appeoval kesay milla apko?
ReplyDeleteSorry sir didnt get you
Delete