To Study Mitosis in Onion Root Tip Cells and Animals Cells (Grasshopper) from Permanent Slides

Have you ever thought about how damaged cells repair? Or how a single-cell zygote forms a complete organism? Mitosis is the kind of cell division through which divisions in somatic cells take place.

All new cells are formed by the division of pre-existing cells. All cells divide into two types- mitosis and meiosis. Somatic cells divide only by mitosis whereas reproductive cells divide by meiosis. In Mitosis chromosome numbers remain the same after division. Meiosis is known as reductional division whereas mitosis is known as equational division and in meiosis, chromosome numbers get halved.

Table of Content

• Aim

• Apparatus Required

• Theory

• Procedure

• Observations

• Results

• Precautions

• Lab Manuals

• Viva Questions

• Practical Based Questions

• Conclusion

Aim

To study mitosis in onion root tip cells and animal cells(grasshopper) from the permanent slide. 

Apparatus Required

• Compound microscope

• Permanent slides

Theory

Cell division is the process of dividing cells. Mainly cell division is of two types - Mitosis and Meiosis. Mitosis usually occurs in somatic cells of eukaryotic organisms. You have studied mitosis in onion roots. All Cell division occurs in two stages- Karyokinesis and cytokinesis. 

• Karyokinesis - It is the process of division of the nucleus

• Cytokinesis - It is the process of division of cytoplasm.

Stages Of Karyokinesis 

There are mainly two phases of karyokinesis. 

Interphase and M phase

The interphase is the longest phase of karyokinesis comprising 95% of the whole cell cycle whereas the M phase comprises only 5% of the cell cycle.

M phase is divided into five steps- 

• Prophase 

• Metaphase 

• Anaphase 

• Telophase

Procedure

• Firstly, place a permanent slide of onion root tip under the microscope

• Observe the different features of dividing cells carefully

• Then place the second slide of grasshopper cells under the microscope

• Observe the characteristics of dividing cells. 

Observation

Under a high-power microscope, we can see the following stages of dividing cells of root tips and grasshoppers in the slides.

• Interphase- In this phase, we can see chromatin fibers in the nucleus. The nuclear envelope and nucleolus can be distinctly seen 

• Prophase- In this stage, we can see chromosomes, and chromatids attached through centromeres. At the end of this phase, the nuclear membrane and nucleolus disappear.

• Metaphase- In this phase, we can see the equatorial plate in which all chromosomes are arranged at the equator. We can see chromosomes very clearly and distinctly in this phase.

• Anaphase- In this phase sister chromatids separate from each other and shift towards opposite poles. These separated chromatids are now referred to as future chromosomes. These future chromosomes appear in different shapes such as V, J, L, and I depending on the location of the centromere.

• Telophase- It is the last phase of nuclear division. In this spindle, fiber disappears and chromosomes condense to form chromatin fibers at two poles. The nuclear membrane and nucleolus reappear and at last two daughter nuclei also appear at the last of this phase.

Stages of Mitosis

Results

All stages of mitosis have been seen in this experiment.

Precautions

• Handle the slides carefully 

• Use high power microscope to observe cell division 

• Always hold the slide by the corner or edge to avoid making it dirty

Lab Manual Questions

1. Mention the phase of cell division in which chromosomes are observed distinctly.

Ans: In metaphase, we can see the chromosomes distinctly and clearly.

2. During metaphase which chemical is used to stop division?

Ans: Colchicine is a chemical that can stop spindle fiber formation and hence stop cell division.

3. Where does mitosis occur?

Ans: Mitosis can occur in vegetative cells.

4. Where do spindle fibers originate from?

Ans: Spindle fiber originates from centriole in animal cells and forms cytoplasm in plant cells.

Viva Question

1. Why is mitosis known as equational division?

Ans: Mitosis is known as equational division because progeny cells have the same number of chromosomes as the parent cell.

2. What are the different stages of interphase?

Ans: There are three stages of interphase - G1 phase, S phase, and G2 phase.

3. What is karyokinesis?

Ans: Karyokinesis is defined as the process of nuclear division.

4. Most of the life of a cell is spent in which phase?

Ans: Most of the life of a cell is spent in Interphase.

5. Define cell cycle.

Ans: The cell cycle is defined as the process or series of events that occur in a cell as the cell divides and grows.

6. What is reductional division?

Ans: Reductional division is a division in which chromosome numbers are reduced to half in progeny cells.

7. What is the quiescent phase?

Ans: Quiescent stage is the stage in which cells do not divide but remain metabolically active.

8. What are the different stages of meiosis?

Ans: Meiosis divides into two types - meiosis I and meiosis II. 

Practical Based Questions

Q1. Which of the following cells undergo a quiescent phase?

1. Stomach cells

2. Heart cells

3. Spleen cells

4. None of the above

Ans: 2. Heart cells

Q2. A centromere has how many kinetochores?

1. 5 kinetochore

2. 1 kinetochore

3. 2 kinetochore

4. None of the above

Ans: 3. (2 kinetochores)

Q3. If there are 48 chromosomes in a cell, then how many chromosomes will be there after meiosis?

1. 48 chromosomes

2. 24 chromosomes

3. 12 chromosomes

4. None of the above

Ans: (2) 24 chromosomes 

Q4. What would be the shape of a metacentric chromosome?

1. S shape

2. V shape

3. X shape

4. None of  the above

Ans: (2) V shape

Q5. The equatorial plate is seen in which phase of mitosis?

1. Metaphase

2. Anaphase

3. Telophase

4. Prophase

Ans: (1) Metaphase

Q6. What is the duration of the interphase of the whole cell cycle?

1. 60%

2. 75%

3. 95%

4. None of the above

Ans: (3) 95%

Q7. Sister chromatids separate in which phase of the cell cycle?

1. Interphase

2. Anaphase

3. Metaphase

4. Prophase 

Ans: (2) Anaphase

Q8. The stage before cell division is known as?

1. Interphase 

2. Metaphase 

3. Telophase

4. None of the above 

Ans: (1)  Interphase

Conclusion

• In this article, we have studied experiments on mitosis in onion root tip cells and animal cells from permanent slides. 

• We have learned that the cell divides into two steps- the first nucleus divides which is known as karyokinesis then the cytoplasm will divides which is known as cytokinesis

• There are five steps of nucleus division - prophase, metaphase, anaphase, and telophase

• We have also learned different characteristics of different stages of mitosis