Cell Division

Failure of chromatids to segregate properly during cell division can result in an abnormal number of chromosomes in the daughter cells. This phenomenon is referred to as "nondisjunction." When nondisjunction occurs, it can lead to a condition known as "aneuploidy." In aneuploidy, cells have an abnormal number of chromosomes, which can result in certain medical conditions, depending on which chromosomes are affected.

To understand why aneuploidy is the correct answer, let's briefly differentiate it from other terms:

• Polyploidy: A condition in which a cell has more than two complete sets of chromosomes (e.g., triploidy, tetraploidy). It is common in plants but generally not viable in animals.
• Euploidy: Having a complete set of chromosomes, which is the normal chromosomal complement in an organism.
• Autopolyploidy: A type of polyploidy where all chromosome sets originate from the same species, leading to multiple sets of the same genome.

Considering these definitions, the correct term for the failure of chromatids to segregate properly is aneuploidy, where cells end up with missing or extra chromosomes.

To solve the problem, we need to understand the stages of mitosis and identify the phase during which the centromeres split and chromatids move to opposite poles.

1. Understanding Mitosis:

Mitosis is a process by which a cell divides to produce two identical daughter cells. It ensures that each daughter cell receives an exact copy of the parent cell's DNA. Mitosis has several phases:

• Prophase: Chromosomes condense, spindle fibers form.
• Metaphase: Chromosomes align at the cell's equator.
• Anaphase: Centromeres split and sister chromatids are pulled apart toward opposite poles.
• Telophase: Chromatids reach the poles, nuclear membranes reform.

2. Key Event in Question:

The phase when centromeres split and chromatids move to opposite poles is anaphase.

3. Why Anaphase?

- In anaphase, the paired sister chromatids separate at their centromeres.
- The separated chromatids, now individual chromosomes, are pulled by spindle fibers to opposite ends of the cell.
- This separation ensures that each new cell will receive one copy of each chromosome.

Final Answer:

The centromeres split and chromatids move to opposite poles during anaphase of mitosis.