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Meiosis I - Reductional Cell Division

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Introduction to Meiosis I

IVSAT 2024

Sexual propagation in living beings happens through the combination of male and female gametes, the sperm and the egg individually. Gametes are haploid in nature, i.e., they contain just a large portion of the quantity of chromosomes. This hereditary substance makes them unique in relation to other body cells. Meiosis prompts the arrangement of haploid cells. Let us have a point by point take a glimpse at meiosis 1 and the various stages and periods of meiosis 1. Mitotic cell division is equational in nature while meiosis is a decreasing division. The notable highlights of meiotic division that make it not quite the same as mitosis are as per the following:- 

  • It happens in two phases of the atomic and cell division as Meiosis I and Meiosis II. DNA replication happens, nonetheless, just a single time. 

  • It includes the matching of homologous chromosomes and recombination between them. 

  • Four haploid girl cells are delivered toward the end, dissimilar to two diploid little girl cells in mitosis. 

  • Meiosis 1 isolates the pair of homologous chromosomes and lessens the diploid cell to haploid. It is isolated into a few phases that incorporate prophase, metaphase, anaphase and telophase.


Meiosis 1 Stages 

The various phases of meiosis 1 can be clarified by the accompanying stages : 

  • Prophase 1 

  • Metaphase 1 

  • Anaphase 1 

  • Telophase 


Phases of Meiosis 1 

The means paving the way to meiosis are like those of mitosis – the centrioles and chromosomes are repeated. The measure of DNA in the cell has multiplied, and the ploidy of the cell continues as before as in the past, at 2n. In meiosis I, the stages are practically equivalent to mitosis: prophase I, metaphase I, anaphase I, and telophase I (underneath figure). Meiosis I continues legitimately to meiosis II without experiencing interphase.


Meiosis I is novel in that hereditary assorted variety is produced through traverse and irregular situating of homologous chromosomes (bivalent chromosomes). What's more, in meiosis I, the chromosomal number is decreased from diploid (2n) to haploid (n) during this procedure. (See figure underneath, where meiosis I starts with a diploid (2n = 4) cell and finishes with two haploid (n = 2) cells.) In people (2n = 46), who have 23 sets of chromosomes, the quantity of chromosomes is diminished considerably toward the finish of meiosis I (n = 23).


Meiosis 1 Prophase 1 

Prophase I is longer than the mitotic prophase and is additionally partitioned into 5 substages.

  • Leptotene 

  • Zygotene 

  • Pachytene 

  • Diplotene 

  • Diakinesis 


The chromosomes start to consolidate and accomplish a reduced structure during leptotene. In zygotene, the blending of homologous chromosomes begins a procedure known as chromosome synapsis, joined by the arrangement of an unpredictable structure called synaptonemal complex. A couple of synapsed homologous chromosomes shapes a complex known as bivalent or quadruplicate.


At the pachytene stage, traverse of non-sister chromatids of homologous chromosomes happens at the recombination knobs. The chromosomes stay connected at the destinations of traverse. 


Diplotene denotes the disintegration of the synaptonemal complex and partition of the homologous chromosomes of the bivalents with the exception of at the destinations of traverse. The X-molded structures shaped during detachment are known as chiasmata.


Diakinesis is set apart by the end of chiasmata and gathering of the meiotic axle to isolate the homologous chromosomes. The nucleolus vanishes and the atomic envelope separates.


Meiosis 1 Metaphase 1 

The bivalents adjust at the tropical plate and microtubules from the contrary posts join to the sets of homologous chromosomes.


Meiosis 1 Anaphase 1 

The two chromosomes of each bivalent discrete and move to the furthest edges of the cells. The sister chromatids are joined to one another.


Meiosis 1 Telophase 1 

The atomic layer returns and is trailed by cytokinesis. This offers access to a dyad of cells. 


How to Start Learning the Meiosis I - Reductional Cell Division? 

You can start learning the Meiosis I - Reductional Cell Division process from Vedantu’s official website. For a user-friendly experience, you can also get access to this concept on our mobile application. The Meiosis I - Reductional Cell Division is the first part of the entire cell division process in eukaryotic cells. Without understanding the process of Meiosis I, you will not be able to understand the process of Meiosis 2. That is why it is important to learn the concept of Meiosis I - Reductional Cell Division. Here are some tips to learn the concept of Meiosis I - Reductional Cell Division:

  • While studying the Meiosis I - Reductional Cell Division for the first time, jot down the important points of the process and make a summarized version of the concept that will help you in quick revision during your exam preparations.

  • Read all the phases of the Meiosis I - Reductional Cell Division and understand their importance. It will give you a clear understanding of the processes that occur during Meiosis I.

  • Once you have learned everything about the Meiosis I - Reductional Cell Division, you should use the exercise questions to practice and check whether you have understood the process clearly or not.

  • Make sure to go through the textbook explanations of the Meiosis I - Reductional Cell Division to get a clear idea of the concept.

  • Use different guides and reference books of Biology to know about the Meiosis I - Reductional Cell Division in detail. These books provide you with a deep insight into the process of cell division and enhance your knowledge.

  • To make the learning process smooth and steady, you can use Vedantu’s online learning platform for free. We provide you with a detailed explanation of the Meiosis I - Reductional Cell Division in a simple language, making it easy to learn and memorize.

  • Before your exam, you should go through the entire concept of Meiosis I - Reductional Cell Division thoroughly as it holds a major portion of the marking distributions in the biology exam.

  • You can test your knowledge of the Meiosis I - Reductional Cell Division by answering questions in sample papers and previous year questions papers of biology.

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FAQs on Meiosis I - Reductional Cell Division

1. What Do You Comprehend by Meiosis? 

Meiosis is the procedure wherein a solitary cell isolates twice to deliver four cells with a large portion of the first measure of chromosomes. 

2. What are the Various Phases of Meiosis I? 

The various phases of meiosis 1 include: 

  • Prophase 

  • Metaphase 

  • Anaphase 

  • Telophase 

The prophase stage is the longest phase of the entire process. In this phase, three events occur, beginning with the condensation of chromatin into chromosomes. Then, the homologous chromosomes come in physical contact with each other. After that, a crossing over of non-sister chromatids of chromosomes occurs. Once the prophase ends, metaphase begins with homologous chromosomes aligning on the equatorial plane. In the third phase i.e. Anaphase, the microtubules diminish and pull one chromosome from each set to opposite poles during the process of disjunction. Lastly, in the telophase, cytokinesis occurs to form two non-identical daughter cells.

3. From where can I learn the concept of Meiosis I - reductional cell division?

You can learn the concept of Meiosis I - Reductional Cell Division from Vedantu’s online learning platform. All you have to do is visit our website or download the mobile application and search for the Meiosis I - Reductional Cell Division. You will get access to this concept on our website entirely free of cost. Vedantu does not even charge you any money to register on our website. Moreover, besides the Meiosis I - Reductional Cell Division, you will find an abundance of study materials for the biology subject. You can learn concepts like Animal cells, algae, budding, ecology, and much more.

4. Why is Meiosis I - reductional cell division important to learn?

The Meiosis I - Reductional Cell Division is one of the most crucial concepts of biology. You have to learn the Meiosis I - Reductional Cell Division to understand how homologous chromosomes are separated and diploid is reduced to haploid. By learning the several stages of the Meiosis I - Reductional Cell Division, you can strengthen your knowledge of cells, which is an essential part of the syllabus. Furthermore, the Meiosis I - Reductional Cell Division carries significant weightage in the exam. So, learning the concept of Meiosis I - Reductional Cell Division will definitely help you score well in your final exams.

5. What is the difference between Meiosis I and Meiosis II?

Meiosis refers to the way eukaryotic cells in plants, animals, and fungi reproduce sexually. Both Meiosis I and Meiosis II have the same number of phases arranged in the same order. However, there is a major difference between both these processes. Meiosis I starts with a diploid parent cell and produces two haploid daughter cells at the end of the process, dividing the number of chromosomes in each cell equally. On the other hand, Meiosis II begins where Meiosis I ends i.e. with two haploid parent cells and produces four haploid daughter cells, dividing the number of chromosomes in each cell equally.


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