Kinetochore

Definition

A kinetochore is a protein structure that forms on the centromere of a chromosome during cell division, serving as the attachment point for spindle fibers. It plays a critical role in the movement of chromosomes during mitosis and cytokinesis by ensuring accurate segregation into daughter cells. This structure is essential for the proper distribution of genetic material, acting as a platform for the interaction between chromosomes and the mitotic spindle.

5 Must Know Facts For Your Next Test

1. Kinetochore formation occurs during prophase, when chromosomes condense and become visible under a microscope.
2. Each chromosome has two kinetochores, one on each sister chromatid, allowing for bi-orientation on the spindle apparatus.
3. Kinetochore proteins interact with microtubules of the mitotic spindle to facilitate chromosome movement during anaphase.
4. The correct attachment of kinetochores to spindle fibers is monitored by a checkpoint mechanism to prevent aneuploidy.
5. Defects in kinetochore function can lead to errors in chromosome segregation, resulting in genetic disorders and cancer.

Review Questions

• How do kinetochores contribute to the process of chromosome segregation during mitosis?
  • Kinetochores are essential for proper chromosome segregation because they serve as attachment points for spindle fibers. During mitosis, these structures help ensure that each sister chromatid is pulled toward opposite poles of the cell. The dynamic interaction between kinetochores and microtubules allows chromosomes to be accurately aligned and separated, which is crucial for generating genetically identical daughter cells.
• Discuss the implications of defective kinetochore function on cellular processes and overall organism health.
  • Defective kinetochore function can lead to improper chromosome segregation, which may result in aneuploidy—an abnormal number of chromosomes in daughter cells. This can have serious implications for cellular processes, leading to diseases such as cancer where cells may proliferate uncontrollably. Additionally, developmental disorders can arise if gametes with incorrect chromosome numbers contribute to fertilization, highlighting the importance of kinetochore integrity for organismal health.
• Evaluate the mechanisms that ensure proper kinetochore-microtubule attachment during mitosis and how they maintain genomic stability.
  • Proper kinetochore-microtubule attachment is ensured through several mechanisms, including tension sensing and error correction pathways. These mechanisms allow kinetochores to detect whether they are correctly attached to microtubules. If misattachments occur, these systems trigger corrective actions, such as detaching and re-attaching to the correct microtubules. This dynamic regulation helps maintain genomic stability by preventing errors in chromosome segregation, which can lead to significant health issues like cancer or genetic disorders.

Related terms

Centromere: The region of a chromosome where the two sister chromatids are joined together, serving as the primary site for kinetochore formation.

Mitotic Spindle: A structure composed of microtubules that segregates chromosomes into daughter cells during mitosis.

Chromatid: One of the two identical halves of a replicated chromosome, which is connected at the centromere before cell division.