CBSE Biology Experiment - Meiosis in Onion Bud Cell or Grasshopper Testis through Permanent Slides
You must be knowing that all germ cells divide by meiosis. One cell after meiosis forms four cells. Meiosis occurs in two stages: meiosis I and meiosis II. Meiosis is known as reductional division because chromosome number is reduced to half in this division. Meiosis leads to variation. Continuous accumulated variation leads to evolution. All of you must have seen the grasshopper or grasshopper diagram. It is widely used for studying meiosis. To know more about this experiment and meiosis continue reading this article.
Table of Content
Aim
Articles Required
Theory
Procedure
Observations
Result
Precautions
Lab Manual Questions
Viva Questions
Practical Based Questions
Summary
Aim
To study meiosis in onion bud cells or grasshopper testis through permanent slides
Articles Required
Permanent slides
Microscope
Theory
Meiosis is a double division that occurs in diploid reproductive cells. It leads to variation and evolution. It occurs in two steps, meiosis I and meiosis II. Meiosis II is the same as mitosis. Meiosis I occurs in two steps: karyokinesis and cytokinesis. Karyokinesis is divided into four stages: prophase, metaphase, anaphase, and telophase. Prophase is of five stages - leptotene, zygotene, pachytene, diplotene, and diakinesis.
Procedure
Fix the permanent slides under the microscope
First, observe slides under a low power microscope, and then high power microscope
Observations
The different stages of meiosis are observed in high-power microscopes. The characteristics of different stages of meiosis are explained below:
Meiosis 1
There are four phases of nuclear division in meiosis 1.
Prophase 1
In meiosis, there are five stages of prophase 1, and it is the longest phase of nuclear division.
Leptotene - in this stage, chromatin fibres become condensed and form a thick thread-like structure called chromosomes
Zygotene - In this stage, homologous chromosomes paired together to form bivalent or tetrad
Pachytene - In this stage, there is a crossing over between non-sister chromatids of homologous chromosomes. In this stage, tetrad appears more clearly.
Diplotene - In this stage, there is the separation of non-sister chromatids except at some sites which are known as chiasmata. A chiasma is an x-shaped structure that represents the site of crossover.
Diakinesis - This is the last stage of meiosis 1. In this stage, homologous chromosomes appear thick and ring-shaped, and the nucleus membrane and nucleolus disappear, and spindle fibres also start to form.
Metaphase 1
In this stage, all paired homologous chromosomes are arranged at the centre of the nucleus, which is known as the equatorial plane, and the equatorial plate can be seen in metaphase 1. Bivalent or tetrad are visible in this stage.
Anaphase 1
In this phase, homologous chromosomes separate from each other and move toward opposite poles. Now each pole has half the number of chromosomes with two chromatids.
Telophase1
It is the last phase of karyokinesis, in this phase chromosomes condensed to form future daughter nuclei, and nucleolus and nuclear membrane reappear.
After karyokinesis, cytokinesis occurs and leads to the formation of two daughter nuclei.
Interkinesis
Interkinesis is defined as the period of rest between meiosis 1 and meiosis 2. Sometimes interkinesis is also known as interphase. But during this phase, there is no DNA replication.
Meiosis II
Two cells formed by meiosis 1 undergo further division to make four cells. There are two stages of meiosis 2, first karyokinesis and cytokinesis. Meiosis II is the same as mitosis.
Prophase II
The chromosomes of daughter cells begin to condense and become thick, and at the last of this stage nucleolus and nuclear membrane begin to disappear.
Metaphase II
The chromosomes are arranged at the equator. All chromosomes are arranged at the equatorial plate. In this stage, two spindle fibers are attached to each chromosome from opposite poles.
Anaphase II
The sister chromatids of homologous chromosomes separate from each other and move toward opposite poles. And each pole receives the same number of chromosomes as that in parent nuclei.
Telophase II
This is the last stage of meiosis. The nuclear membrane and nucleolus reappear and chromosomes condensed to form future daughter nuclei.
Stages of meiosis
Result
The various stages of meiosis are distinctly seen under the microscope.
Precautions
Following precautions must be taken while experimenting
Slides must be cleaned before use
Place slides under the microscope carefully.
Lab Manual Questions
Q1. What is the significance of Meiosis?
Ans: meiosis is necessary for evolution, and also it maintains chromosome numbers in sexually reproducing organisms.
Q2. What is crossing over?
Ans: Crossing over is the process of exchanging genetic material between non-sister chromatids of homologous chromosomes.
Q3. At what stages does crossing over take place?
Ans: Crossing over takes place in the pachytene stage.
Viva Questions
Q1. What is meiosis?
Ans: It is a type of reductional division in which chromosome numbers get halved. It occurs in sexually reproducing organisms. Gametes are formed by reductional division.
Q2. What is the purpose of meiosis in plants?
Ans: Meiosis is a type of reductional division used to produce gametes or sex cells by meiosis. In this, four cells are produced from one cell.
Q3. What is spermatogenesis?
Ans: Spermatogenesis is defined as the process of formation of sperms from primordial germ cells. These cells are formed by meiosis division.
Q4. Why is meiosis II known as equational division?
Ans: Meiosis II is equational division because, in meiosis, chromosome number remains the same in divided cells.
Q5. What are the different stages of meiosis?
Ans: There are many different stages of meiosis. These stages are given here- interphase, prophase1, metaphase 1, anaphase1, telophase1, cytokinesis, interphase II, prophase II, metaphase II, anaphase II, and telophase II.
Q6. Does meiosis occur in an onion cell?
Ans: Onion root tip is only used for mitotic study, as they are meristematic cells and do not exhibit meiosis.
Q7. In meiotic division, how many times DNA replication occurs?
Ans: In meiosis, replication occurs only one time, whereas division occurs twice. Meiosis I and Meiosis II are two divisions of meiosis.
Q8. What is the main function of meiosis?
Ans: Meiosis is used to produce gamete cells from germ cells. Here one germ cell divides to form four gametes. And in meiosis, the chromosome number is reduced to half.
Practical Based Questions
Q1. Why is a grasshopper used in the study of meiosis?
Due to smaller chromosome size
Due to larger chromosome size
Due to more chromosome
None of the above
Ans: 2. Due to larger chromosome size
Q2. In which cells of testis meiosis take place?
Spermatid
Spermatogonia
Spermatocytes
Sperm
Ans: 3. Spermatocytes
Q3. Who invented meiosis
Hertwig
Robert brown
Landsteiner
None of the above
Ans: 1. Hertwig
Q4. A bivalent consists of how many chromatids and chromosomes
1 chromosome and 4 chromatids
1 chromosome and 2 chromatids
2 chromosomes and 4 chromatids
None of the above
Ans: 3. 2 chromosomes and 4 chromatids.
Q5. During cell division spindle fibers attached to which parts of chromosomes
Kinetochore
Centromere
Telomere
None of the above
Ans: 1. Kinetochore
Q6. Continuous variations are produced in which division
Mitosis
Meiosis
Both of the above
None of the above
Ans: 2. Meiosis
Q7. How many cells are formed after one meiosis?
2 cells
6 cells
3 cells
4 cells
Ans: 4. 4 cells
Q8. If there are four chromosomes in a cell, then after meiosis 1 how many chromosomes will be there?
4 chromosomes
3 chromosomes
2 chromosomes
None of the above
Ans: 3. 2 chromosomes.
Conclusion
In this article, we have discussed meiosis in onion bud cells or Grasshopper cells
We have seen various stages of meiosis under a microscope
There are two phases of meiosis. Meiosis I and meiosis II. The Karyokinesis of meiosis takes place in four steps
Meiosis is necessary for variation and evolution
Meiosis II is the same as mitosis.
FAQs on To Study the Stages of Meiosis in Onion Bud Cells or Grasshopper Testis Through Permanent Slides
1. What are the most important stages of meiosis observed in onion bud cells and grasshopper testis for CBSE Class 12 board exams?
The most important stages of meiosis to focus on include:
- Prophase I: Subdivided into leptotene, zygotene, pachytene, diplotene, and diakinesis. Pay special attention to crossing over in pachytene.
- Metaphase I: Bivalents/tetrads align at the equatorial plane.
- Anaphase I: Homologous chromosomes separate, reducing the chromosome number by half.
- Telophase I and Cytokinesis: Formation of two haploid nuclei.
- Meiosis II stages are similar to mitosis and should also be revised.
2. Which questions related to meiosis in onion or grasshopper are frequently asked for 3-mark and 5-mark sections in CBSE Biology exams?
Frequently asked questions include:
- Describe the stages of prophase I of meiosis with diagrams (5-mark, HOTS).
- Explain how crossing over leads to genetic variation (3-mark).
- Compare and contrast meiosis I and meiosis II (5-mark).
- Explain why grasshopper testis is preferred for studying meiosis (3-mark).
- Discuss the significance of meiosis in sexually reproducing organisms (3-mark).
3. What important concepts should be highlighted in answers about meiosis for maximum marks?
To maximize marks, ensure that answers highlight:
- Reductional division in meiosis I and equational division in meiosis II.
- The precise sequence and characteristics of each stage.
- Genetic variation due to crossing over and independent assortment.
- Accurate biological terminology and clear, labeled diagrams.
- The difference between mitosis and meiosis, especially chromosome number changes.
4. Why is the grasshopper testis specimen considered ideal for the study of meiosis in board practical exams?
Grasshopper testis is ideal because chromosomes are larger, making the stages of meiosis more distinct and easier to identify under a microscope. This helps visualize bivalent formation and crossing over, which are key for board practical assessments.
5. What is the role of crossing over during meiosis, and at which stage does it happen?
Crossing over occurs during the pachytene stage of prophase I, when non-sister chromatids of homologous chromosomes exchange genetic material. This process increases genetic variation, which is essential for evolution and adaptation in sexually reproducing organisms.
6. How do previous board trends reflect the importance of meiosis questions in CBSE Class 12?
Meiosis is a recurring topic, often appearing as 3-mark, 5-mark, and practical-based questions. Diagrams and identification of stages, differences from mitosis, and critical terms like chiasma and bivalent frequently feature in board papers. Practicing past year questions helps identify these trends.
7. What are common mistakes students make while answering meiosis-based questions in CBSE Biology exams?
Common mistakes include:
- Confusing stages of mitosis and meiosis.
- Incorrectly labeling or identifying diagrams of meiosis stages.
- Forgetting to mention the significance of crossing over and reduction division.
- Omitting key differences between meiosis I and II.
8. Why does meiosis lead to genetic variation, and how is this evaluated in board exams?
Meiosis generates genetic variation through crossing over during pachytene and independent assortment of chromosomes. CBSE boards evaluate this by asking students to explain these processes, often in 3-mark questions or through diagram labeling where variations and chiasmata formation must be identified.
9. How are important specimen handling precautions assessed in practical and theory questions about meiosis?
Precautions are tested in both theory and practical exams. Key points include:
- Always use a clean, dry permanent slide.
- Focus carefully, starting with low and moving to high power on the microscope.
- Handle slides gently to avoid breakage.
- If asked, state the importance of these steps for clear observation and accurate identification of meiosis stages.
10. What is the significance of meiosis in maintaining chromosome number across generations, and how can this concept appear as a high-order thinking skill (HOTS) question?
Meiosis reduces the chromosome number by half in gametes, ensuring that fertilization restores it in the next generation. This maintains chromosome stability across species. HOTS questions may ask you to apply this by predicting outcomes if meiosis failed, or by comparing genetic consequences in mitosis versus meiosis.
