Question

Some studies suggest that in patients with Alzheimer's disease, there is a defect in the way the spindle apparatus attaches to the kinetochore fibers. At which stage of mitotic division would you expect to see this problem?

Short answer

Metaphase

Step-by-step solution

Understand the spindle apparatus and kinetochore fibers

The spindle apparatus is a structure made of microtubules which segregates chromosomes during cell division. The kinetochore fibers attach to the chromosomes at the kinetochore, which is a protein structure on the chromosome.

Identify the stages of mitosis

Mitosis consists of several stages: prophase, metaphase, anaphase, and telophase. Each stage has specific events related to the arrangement and separation of chromosomes.

Determine the relevant stage for spindle attachment

Kinetochore fibers must attach properly to the spindle apparatus for chromosomes to align correctly. This attachment occurs during metaphase, where chromosomes align at the metaphase plate.

Reason about the stage where defects would be noticeable

If there is a defect in the attachment of spindle apparatus to kinetochore fibers, it would prevent chromosomes from aligning correctly at the metaphase plate. Thus, the defect would be most evident during metaphase.

Key concepts

Spindle Apparatus

The spindle apparatus is crucial for cell division. It is composed of microtubules, which are tiny, tube-like structures. These microtubules organize into a spindle-shaped structure during cell division. Their main job is to help segregate chromosomes into the two daughter cells.
Think of microtubules as ropes. They attach to chromosomes at specific points called kinetochores. The spindle apparatus makes sure each new cell gets the right number of chromosomes.
In Alzheimer's disease, studies suggest there might be problems with how the spindle apparatus works. This can lead to errors in chromosome separation, which affects cell function.

Kinetochore Fibers

Kinetochore fibers play an important role in chromosome movement during mitosis. These fibers are actually microtubules that connect to the kinetochores. A kinetochore is a protein structure located on the chromosome.
Kinetochore fibers act like ropes pulling chromosomes into the right position for division. If these fibers do not attach correctly, chromosomes can be misaligned. This misalignment leads to problems in cell division.
In Alzheimer's disease, defects in the attachment of kinetochore fibers can disrupt the normal process of mitosis. This disruption can contribute to the progression of the disease by causing errors in cell division.

Metaphase

Metaphase is one of the key stages of mitosis. During this phase, chromosomes align at the cell’s equator, forming a structure known as the metaphase plate. Proper alignment ensures that each daughter cell will receive an identical set of chromosomes.
The spindle apparatus attaches to chromosomes through kinetochore fibers in this phase. If there is a problem with the spindle attachment, chromosomes can fail to align correctly at the metaphase plate.
In the context of Alzheimer's disease, any defect in attachment would be most noticeable during metaphase. This stage is critical because any errors here can lead to improper chromosome separation and ultimately cell malfunction. Understanding how these defects occur can help in exploring potential treatments for Alzheimer's.