Spindle fiber

Spindle fiber is a protein structure that forms during cell division. It is responsible for separating the chromosomes into the daughter cells during both mitosis and meiosis.

Structure

Spindle fibers are composed of microtubules, which are part of the cell's cytoskeleton. These microtubules originate from the centrosome, a structure often referred to as the "microtubule organizing center". During cell division, two centrosomes move to opposite ends of the cell and begin to generate the spindle fibers.

Function

The primary function of the spindle fiber is to ensure that each daughter cell receives an equal number of chromosomes during cell division. The spindle fibers attach to the kinetochore, a protein structure on the chromatid, and move the chromosomes to the equatorial plane of the cell. Once all the chromosomes are aligned, the spindle fibers shorten and pull the sister chromatids apart, moving them towards the opposite poles of the cell.

Role in Cell Division

In mitosis, the spindle fibers play a crucial role in aligning the chromosomes along the middle of the cell before they are separated into the two daughter cells. In meiosis, spindle fibers are also involved in the movement and separation of homologous chromosomes and sister chromatids during the two divisions.

Clinical Significance

Abnormalities in spindle fiber formation can lead to errors in chromosome separation, resulting in cells with an abnormal number of chromosomes, a condition known as aneuploidy. This is often associated with several types of cancer and genetic disorders such as Down syndrome.

See Also

• Cell cycle
• Cytokinesis
• Centriole
• Microtubule