Mitosis – Frequently Asked Questions and Answers

What is Mitosis?

Answer – Mitosis is a type of cell division that results in the formation of two identical daughter cells each with the same number of chromosomes as the parent cell. It is an important process in the growth and repair of tissues in multicellular organisms and  asexual reproduction in some single-celled organisms.

The process of mitosis can be divided into several distinct phases – 

  • Prophase: The chromosomes condense and become visible as discrete structures, and the nuclear envelope breaks down.
  • Prometaphase: The spindle apparatus forms and the chromosomes attach to the spindle fibers.
  • Metaphase: The chromosomes align at the center of the cell and are held in place by the spindle fibers.
  • Anaphase: The chromosomes separate and are pulled to opposite ends of the cell.
  • Telophase: A new nuclear envelope forms around each set of chromosomes and the chromosomes decondense.
  • Cytokinesis: The cytoplasm divides, resulting in the formation of two separate daughter cells.

Mitosis is a carefully regulated process that is controlled by a variety of different proteins and biochemical pathways. Errors in mitosis can lead to the formation of abnormal cells, which can contribute to the development of diseases such as cancer.

Also Check – Why is Mitosis called the “Equational Division” and Meiosis is called the “Reduction Division”?

Also Check- 12 Important Significance of Mitosis

How is the Chromosome number Maintained in Mitosis ? 

Answer – The chromosome number is maintained in mitosis through a series of precise and regulated steps. During the process of interphase the DNA is replicated, resulting in two identical copies of each chromosome. In the process of  mitosis these replicated chromosomes are separated and distributed evenly to each of the two daughter cells.

Distribution of an equal number of chromosomes to the daughter cell is accomplished through the role of the spindle apparatus. A spindle apparatus  is a complex structure composed of microtubules and associated proteins. Spindle apparatus helps to align the chromosomes at the center of the cell and then pulls the chromosomes apart. It  ensures that each daughter cell receives a complete and identical set of chromosomes.

It is important to maintain the chromosome number during cell division because it ensures that the genetic information is passed on accurately from one generation of cells to the next. If the chromosome number is not maintained it  can result in a condition known as aneuploidy. Aneuploidy is the cell that has an abnormal number of chromosomes.  It can lead to a variety of genetic disorders and is also a hallmark of cancer cells.

Also Check – What is the Role of Chromosomes in Cell Division ?

Also Check – Mitosis In Plant Cell and Animal Cell- Differences and Similarities

Can mitosis occur without Cytokinesis? 

Answer – No, mitosis cannot occur without cytokinesis. Cytokinesis is the final stage of mitosis, during which the cytoplasm of the cell divides and the two daughter cells are physically separated from each other. It is an essential part of the mitotic process, as it ensures that the genetic information that was separated and divided among the chromosomes during the earlier stages of mitosis is maintained in the daughter cells.

If cytokinesis does not occur, the chromosomes would be separated, but the cytoplasm would remain undivided, resulting in a single cell with multiple nuclei. This would result in an abnormal cell structure, and the daughter cells would not be able to function normally.

Therefore, it is safe to say that mitosis and cytokinesis are tightly linked and cannot occur without each other. Cytokinesis is necessary to complete the process of mitosis and to ensure the proper formation and functioning of the daughter cells.

Also Check – 7 Important Difference Between Mitosis and Meiosis

How does Cytokinesis differ in Plants and Animals ? 

Answer- Cytokinesis is the final stage of mitosis during which the cytoplasm of the cell divides and the two daughter cells are physically separated from each other. Cytokinesis in plant and animal cells has following difference – 

Cytokinesis in plant cell and animal cell

In animal cells cytokinesis occurs by the formation of a contractile ring composed of actin and myosin filaments. Contractile ring constricts and pinches the cell membrane to separate the cytoplasm into two distinct cells. This process is known as cleavage and is unique in animal cells mitosis. 

In plant cells cytokinesis occurs differently due to the presence of a cell wall. The division of the cytoplasm is achieved by the formation of a cell plate. Cell plate grows from the center of the cell towards the cell wall. As the cell plate grows it eventually fuses with the cell wall by forming a new cell wall and dividing the cytoplasm into two distinct cells.

 Why is Mitosis Important?

Answer – Mitosis is the process of cell division that results in the formation of two genetically identical daughter cells.

Mitosis plays a important role in following many important biological functions – 

  • Tissue growth and repair –  Mitosis allows cells to divide and multiply, leading to an increase in tissue size. This is important in the growth and development of organisms as well as in the repair of damaged tissues.
  • Asexual reproduction – Some organisms like bacteria and yeast reproduce asexually through mitosis. In these organisms a single cell divides to form two genetically identical daughter cells, which can then go on to divide and multiply which results in the formation of a population of genetically identical cells.
  • Maintenance of chromosome number  – Mitosis ensures that the number of chromosomes is maintained from one generation of cells to the next. In the process of mitosis the chromosomes are accurately replicated and separated which results in two daughter cells with the same number of chromosomes as the original cell.
  • Generation of specialized cells –  During the development of multicellular organisms, some cells undergo mitosis to generate specialized cells like  muscle cells, nerve cells, blood cells, etc.  This allows for the formation of tissues with specific functions and are necessary for the proper functioning of the organism.
  • Cancer – Mitosis also plays a role in the development of cancer. In some cases, the normal control mechanisms that regulate cell division can break down, leading to the uncontrolled proliferation of cells. This uncontrolled cell division is a hallmark of cancer and is one of the key factors that contributes to the development and progression of the disease.

Also Check – Why is Mitosis necessary for Growth?

How do Mitosis Repair Cells ?

Answer – Mitosis itself does not repair cells. 

Mitosis is a process of cell division that generates two genetically identical daughter cells. The process of cell division through mitosis is an essential part of repairing and regenerating damaged tissues.

When the cell is damaged it activates various cellular pathways that detect and repair the damage. 

Example- In the DNA damage response. It has a series of cellular pathways that detect and repair damaged DNA. If the damage is severe the cell may undergo apoptosis (programmed cell death) to prevent the propagation of mutations.

If the damage is repairable, the cell may activate the cell cycle to produce new cells. The cell cycle is the series of events that lead to cell division. It will go through phases of interphase (G1, S, and G2) and Mitosis. 

In Interphase the cell replicates its DNA and prepares for mitosis.

In mitosis the replicated chromosomes are divided into two identical sets, and the cell membrane pinches inward to divide the cytoplasm into two daughter cells. These new cells are genetically identical to the parent cell and can replace damaged or lost cells. 

Mitosis is especially important for the regeneration of tissues with high turnover rates.

In which mitosis phase cytokinesis occurs ? 

Answer – Cytokinesis is the final stage of cell division . It occurs after the chromosomes have been separated during the process of mitosis. 

Cytokinesis begins in the late stages of anaphase or early stages of telophase and continues until two distinct daughter cells have formed.During the process of  cytokinesis the cytoplasm of the cell is divided into two parts, which are divided into the two daughter cells. 

The timing of cytokinesis is tightly regulated and occurs only after the chromosomes have been properly segregated into the two daughter cells. If cytokinesis occurs before the chromosomes have been completely separated, the resulting daughter cells will have an abnormal number of chromosomes and may not be viable.

Can mitosis occur in both haploid and diploid cells?

Answer- In Diploid Cells mitosis plays an important role in growth, tissue repair, and cell replacement. In the process of mitosis, the diploid cell divides into two identical daughter cells each with the same number of chromosomes as the parent cell. DNA replicates and then divides into two identical daughter cells. In diploid cells the resulting daughter cells will also be diploid with two sets of chromosomes.

In Haploid Cells mitosis occurs but the resulting daughter cells will also be haploid. Mitotic division in haploid cells is important for the growth of gametes in multicellular organisms.

Note- Mitosis can occur in both haploid and diploid cells but meiosis which is another type of cell division can occur only in diploid cells.

Where does Mitosis occur in a plant

Answer – Mitosis occurs in various parts of a plant. It occurs in 

Somatic cells – the non-reproductive cells of plants

Meristematic cells – the cells that give rise to new cells in plant growth and development.

  • In Somatic cells mitosis can occur in roots, stems, leaves, and other non-reproductive plant tissues. These cells undergo mitosis to help the plant grow , develop, and  repair any damaged tissues.
  • In meristematic cells mitosis occurs in the apical meristems.They are located at the tips of roots, shoots, and in the lateral meristems . Lateral meristems are responsible for increasing the girth of stems and roots. These cells undergo rapid mitotic divisions to produce new cells that differentiate into various types of plant tissues.

Where does Mitosis occur in Animals?

Answer – Mitosis is an important process for the growth, development, and maintenance of animal cells and tissues. Mitosis occurs in a variety of cell types and tissues throughout the body.

  • Mitosis occurs in somatic cells – the non-reproductive cells of the body and in cells that make up various tissues and organs.
  • In somatic cells mitosis occurs in a variety of tissues like skin, muscle, and blood vessels. 
  • These cells undergo mitosis to replace damaged or dead cells and to help the body to grow and develop.
  • Mitosis also occurs in cells that make up various organs like the liver, kidneys, and lungs. 
  • These cells undergo mitosis to help maintain the structure , function of the organs and to repair any damaged tissues.
  • Mitosis also occurs in germ cells. They are the cells that give rise to eggs and sperm. 
  • Germ cells undergo mitosis to produce more cells that eventually differentiate into specialized cells that form eggs and sperm.

Where does Mitosis occur in Humans?

Answer- Mitosis is an important process for the growth, development, and maintenance of human cells and tissues. Mitosis occurs in various tissues and organs throughout the human body. 

  • Mitosis occurs in somatic cells. They are the non-reproductive cells of the body, as well as in cells that make up various tissues and organs.
  • In somatic cells mitosis occurs in a variety of tissues like skin, muscle, and blood vessels. Somatic cells undergo mitosis to replace damaged or dead cells, and to help the body grow and develop.
  • Mitosis also occurs in cells that make up various organs like the liver, kidneys, and lungs. These cells undergo mitosis to help maintain the structure , function of the organs and to repair any damaged tissues.
  • Mitosis also occurs in germ cells. Germ cells are the cells that give rise to eggs and sperm. In females mitosis occurs during the development of ova. Ova  are immature eggs that are stored in the ovaries. In males mitosis occurs in the testes to produce sperm.

Also Check – Where does Mitosis and Meiosis occur ?

Which phase of Mitosis is the Longest ? Explain why? 

Answer – Prophase 

The length of the different phases of mitosis can vary depending on the specific cell type and the stage of development.prophaseis the phase that takes the longest due to the complex processes involved in chromosomal condensation and spindle fiber formation.

Explanation 

In the prophase phase  the chromatin in the nucleus condenses into visible chromosomes, the nuclear membrane dissolves, and the spindle fibers begin to form. These processes require a significant amount of energy and time to complete as the cell undergoes significant changes to prepare for cell division.This is the reason why prophase is the longest phase of mitosis.the other stages of mitosis (prometaphase, metaphase, anaphase, and telophase) typically occur relatively quickly once prophase is complete.

In some casesProphase may be prolonged if there are issues with chromosomal alignment or if the spindle fibers are not properly attached to the chromosomes. These issues can trigger checkpoint controls that delay progression to the next phase. It can further extend the duration of prophase.

Note – The duration of each stage can vary depending on the specific cell type and the conditions under which the cell is growing.

 Which Mitosis Phase is the Shortest? Explain why 

Answer- Anaphase

Length of each phase of mitosis can vary depending on the cell type and conditions.Anaphase is generally the shortest phase due to the relatively simple and rapid separation of the sister chromatids.

Explanation

In the process of anaphase the sister chromatids (which make up each duplicated chromosome) separate and are pulled toward opposite ends of the cell by the spindle fibers.

Compared to the other phases of mitosis, anaphase is relatively straightforward and rapid. While the separation of the sister chromatids requires significant energy and coordination, the process itself typically takes only a few minutes to complete in most cells.

Is DNA replicated in Mitosis?

Answer – DNA replication occurs in the S phase of interphase, which precedes mitosis. In the process of mitosis the replicated chromosomes are distributed to the daughter cells but no DNA replication occurs.

In the S phase the DNA molecule unwinds and separates into two strands.Each strand serves as a template for the synthesis of a new complementary strand, resulting in two identical copies of the original DNA molecule.

In the process of  mitosis, DNA is condensed and organized into chromosomes to be distributed to the daughter cells. The replicated chromosomes condense and align at the metaphase plate. The sister chromatids are separated and pulled to opposite poles of the cell during Anaphase. And finally the nuclear envelope forms around the separated chromosomes.the cell undergoes cytokinesis to complete cell division.

Also Check – Can there be Mitosis without DNA Replication in S phase ?

In which mitosis phase DNA Replicates?

Answer- DNA replication does not occur in mitosis. 

DNA replication occurs during the S (synthesis) phase of interphase. S phase is the period of the cell cycle that precedes Mitosis. 

In the process of  interphase the  cell grows and replicates its DNA in preparation for cell division. The S phase is the stage of interphase where DNA replication occurs which results in the duplication of the genetic material.

The duplicated chromosomes resulting from DNA replication are then organized and separated in the process of MitosisWhich leads to the formation of two genetically identical daughter cells

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Also Check- 5 Important Function of Mitosis

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