What is Meiosis ? || Difference between Meiosis 1 and Meiosis 2 || Matric to F.sc Biology Lectures скачать в хорошем качестве

What is Meiosis ? || Difference between Meiosis 1 and Meiosis 2 || Matric to F.sc Biology Lectures

Meiosis | Cell Division | 3d animation | animation video | #animation #meiosis #celldivision ✅️✅️✅️TOPICS IN THIS VIDEO ✅️ ✅️✅️ 00:00.Introduction 02:11.Meiosis 06:31.Gametes 09:02.Karyokinesis 1 09:42.Prophase 1 11:46.Homologous Chromosomes 12:55.Synapsis 13:34.Crossing over of Non sister Chromatids 19:26:Metaphase 1 20:55.Anaphase 1 21:43.Telophase 1 22:50.Cytokinesis 1 What is Mitosis full conceptual urdu Lecture    • What is Mitosis? || Stages of Mitosis || E...   ✅️✅️All previous Lectures ✅️✅️✅️    • BIOLOGY CHAPTER 01 CLASS 9th   Biology Class 9th 2nd Chapter all Videos    • SOLVING BIOLOGICAL PROBLEM CHAPTER 02 CLAS...   Biology Class 9th 3rd Chapter all Videos    • BIODIVERSITY CHAPTER 03 CLASS 9th   Biology Class 9th 4th Chapter all Videos    • CELL AND TISSUE CHAPTER 04 CLASS 9th   Biology Class 9th 5th Chapter all Videos    • CELL CYCLE CHAPTER 05 CLASS 9th   ✅️✅️✅️MEIOSIS✅️✅️✅️ Prophase I During prophase I, chromosomes condense and become visible inside the nucleus. As the nuclear envelope begins to break down, homologous chromosomes move closer together. The synaptonemal complex, a lattice of proteins between the homologous chromosomes, forms at specific locations, spreading to cover the entire length of the chromosomes. The tight pairing of the homologous chromosomes is called synapsis. In synapsis, the genes on the chromatids of the homologous chromosomes are aligned with each other. The synaptonemal complex also supports the exchange of chromosomal segments between non-sister homologous chromatids in a process called crossing over. The crossover events are the first source of genetic variation produced by meiosis. A single crossover event between homologous non-sister chromatids leads to an exchange of DNA between chromosomes. Following crossover, the synaptonemal complex breaks down and the cohesin connection between homologous pairs is also removed. At the end of prophase I, the pairs are held together only at the chiasmata; they are called tetrads because the four sister chromatids of each pair of homologous chromosomes are now visible. Metaphase I During metaphase I, the tetrads move to the metaphase plate with kinetochores facing opposite poles. The homologous pairs orient themselves randomly at the equator. This event is the second mechanism that introduces variation into the gametes or spores. In each cell that undergoes meiosis, the arrangement of the tetrads is different. The number of variations is dependent on the number of chromosomes making up a set. There are two possibilities for orientation at the metaphase plate. The possible number of alignments, therefore, equals 2n, where n is the number of chromosomes per set. Given these two mechanisms, it is highly unlikely that any two haploid cells resulting from meiosis will have the same genetic composition. Telophase I and Cytokinesis In telophase I, the separated chromosomes arrive at opposite poles. In some organisms, the chromosomes decondense and nuclear envelopes form around the chromatids in telophase I. Then cytokinesis, the physical separation of the cytoplasmic components into two daughter cells, occurs without reformation of the nuclei. In nearly all species of animals and some fungi, cytokinesis separates the cell contents via a cleavage furrow (constriction of the actin ring that leads to cytoplasmic division). In plants, a cell plate is formed during cell cytokinesis by Golgi vesicles fusing at the metaphase plate. This cell plate will ultimately lead to the formation of cell walls that separate the two daughter cells. Two haploid cells are the end result of the first meiotic division. The cells are haploid because at each pole there is just one of each pair of the homologous chromosomes. Therefore, only one full set of the chromosomes is present. Although there is only one chromosome set, each homolog still consists of two sister chromatids.