How Many Chromatids Are Present in Metaphase After Telophase?

Mitosis is a process of cell division that plays a crucial role in growth, repair, and asexual reproduction. During mitosis, the cell divides into two genetically identical daughter cells. Understanding the number of chromatids present during each phase of mitosis is essential for students of biology and researchers in the field of genetics. One common question is: how many chromatids will be present in metaphase if a cell has 21 pairs of chromosomes just after completing mitotic telophase?

In this article, we’ll break down the stages of mitosis and explain the correct answer to this common question.

Mitosis and Its Phases

Before diving into the number of chromatids in metaphase, let’s understand the key stages of mitosis. These include:

1. Prophase: Chromosomes condense and become visible.

2. Metaphase: Chromosomes align at the cell’s equatorial plate.

3. Anaphase: Chromatids separate and move toward opposite poles.

4. Telophase: Chromatids reach the poles, and the cell starts dividing.

The question refers to a situation where the cell carries 21 pairs of chromosomes after the completion of telophase. Now, let’s calculate how many chromatids will be present during metaphase, the phase where chromosomes align at the middle of the cell.

Step-by-Step Calculation

1. Understanding Chromosomes at Telophase:

   • After telophase, the cell has completed the process of dividing its genetic material into two sets.

   • The cell contains 21 pairs of chromosomes. Since each pair consists of two chromosomes, the total number of chromosomes is:

     $$21\text{pairs}\times 2=42\text{chromosomes}.$$

   • At this stage, each chromosome consists of two chromatids joined at the centromere.

2. Chromatids in Metaphase:

   • During metaphase, the chromosomes are still composed of two chromatids (since DNA replication occurs prior to mitosis, during the S-phase).

   • Since there are 42 chromosomes (as established above), and each chromosome is made up of 2 chromatids, the total number of chromatids in metaphase is:

     $$42\text{chromosomes}\times 2\text{chromatids per chromosome}=84\text{chromatids}.$$

Conclusion: The Correct Answer

Thus, the total number of chromatids in metaphase will be 84 chromatids when a cell has 21 pairs of chromosomes just after the completion of telophase. The correct answer is:

(3) 84

Understanding the number of chromatids during different stages of mitosis is essential for grasping how genetic material is distributed during cell division. This knowledge is vital not only for students studying biology but also for researchers working in genetics and cellular biology.

Why Is This Important?

The concept of chromatids in mitosis is fundamental to understanding the cell cycle. By learning how chromatids behave during each phase of mitosis, we can better understand how cells replicate and divide. This knowledge is essential in various fields, including genetics, cancer research, and developmental biology. For example, errors during mitosis, such as the improper separation of chromatids, can lead to genetic disorders and cancer.

By grasping how chromatids are distributed during metaphase, we gain insights into the mechanisms that ensure genetic stability during cell division.

Final Thoughts

In summary, after the completion of telophase, if a cell carries 21 pairs of chromosomes, there will be 84 chromatids during metaphase. This is because each chromosome, made up of two chromatids, is present in a total of 42 chromosomes, leading to a count of 84 chromatids in metaphase. Understanding these stages is critical for anyone studying the fundamentals of cell division and genetics.