Bio

• Session 13: Cell Division: Sexual reproduction and meiosis

  
• Course: Biology, Foundation Year Department, Academic Year: 2023-2024
• This talk is about cell division, sexual reproduction, and meiosis

  
• Sexual reproduction

  The genetic contribution of two cells

  
• Meiosis

  A division process from a diploid cell with two sets of chromosomes (2n) to haploid cells with a single set of chromosomes
• Meiosis


  1. Meiosis I: Homologous pairs separate

  2. Meiosis II: Sister chromatids separate
• Meiosis

  • Used for the production of gametes (sex cells, or sperm and eggs)
  • To make daughter cells with exactly half as many chromosomes as the starting cell

  
• When a sperm and an egg join in fertilization

  The two haploid sets of chromosomes form a complete diploid set: a new genome

  
• Meiosis involves a two-step division process
• After meiosis I, the cell has n=23 chromosomes
• After meiosis II, the cell has 23 chromosomes (Haploid)
• Meiosis


  • Occurs during gamete formation
  • Produces cells with half the normal number of chromosomes
• Phases of meiosis


  1. Prophase I

  2. Metaphase I

  3. Anaphase I

  4. Telophase I
• In prophase I, homologous chromosomes pair along their entire length during synapsis
• Crossing over occurs during prophase I, forming chiasmata which hold homologous chromosomes together
• In metaphase I, pairs of homologous chromosomes align at the equator of the cell
• In anaphase I, homologous pairs are pulled apart, with one duplicated homologous going to one pole and the other to the other pole
• In telophase I, the separated homologues form a cluster at each pole of the cell, and the nuclear envelope re-forms around each daughter cell nucleus
• After meiosis I, the two daughter cells have half the number of chromosomes of the original cell
• Each chromosome in the daughter cells consists of two sister chromatids, but the sister chromatids are not identical due to crossing over
• រ ៃិងជាប់គ្នាម ាតាេបម្តាយ


  1. បមងកើតបាៃជាត្ក៉ូម ាទីតបួៃ ឬមគអាចម ាថា មតត្តា

  2. បមងកើតឱ្យមាៃបាតុេ៉ូត ត្កសុីញអ៉ូមវី

  3. ម ាចុងនៃវគគត្ប៉ូផាសI
• ភ្នាសនណេយ ៉ូរលាយបាត់


  ត្តយ ៉ូងអាត្ក៉ូម ាទិចមលចម ើង
• ហេតាផាសI

  • មតត្តាទាំងអស់ ណដលតមត្េៀបគ្នាមលើបលង់មអកេាទ័រ ភ្ជាប់ខ្លួៃម ាៃឹងត្តយ ៉ូងអាត្ក៉ូម ាទិច ម ាយសង់ត្ត៉ូណេររបស់វា
• អាណាផាសI

  • ត្ក៉ូេ ៉ូស៉ូេអ៉ូេ ៉ូ ូកនៃគ៉ូរៃីេួយៗផតាច់មចញពីគ្នា ម ើយម្េើដំមណើរម ាកាៃ់ប ៉ូល្ទុយគ្នារបស់មកាសិកា
  • ត្ក៉ូម ាទីតទាំងពីររបស់ត្ក៉ូេ ៉ូស៉ូេៃីេួយៗេិៃផតាច់មចញពីគ្នាមទ
  • ម ាប ៉ូលមកាសិកាៃីេួយៗមាៃចំៃួៃត្ក៉ូេ ៉ូស៉ូេអាបលូអ ៊ីត

  
• ហ ឡូផាសI

  • សុីត៉ូបលាសណចកខ្លួៃបាៃមកាសិកាក៉ូៃពីរ
  • មកាសិកាក៉ូៃៃីេួយៗ ទទួលបាៃត្ក៉ូេ ៉ូស៉ូេណតេួយពីគ៉ូអ៉ូេ ៉ូ ូក
  • មកាសិកាក៉ូៃមាៃចំៃួៃត្ក៉ូេ ៉ូស៉ូេណតពាក់ក្តាលនៃចំៃួៃត្ក៉ូេ ៉ូស៉ូេរបស់មកាសិកាមេ
  • ត្ក៉ូេ ៉ូស៉ូេៃីេួយៗមាៃត្ក៉ូម ាទីតពីរ
  • ត្តយ ៉ូងអាត្ក៉ូម ាទិចរលាយបាត់

  
• ម ាមពលបញ្ចប់មត ូផាសភ្លាេ មកាសិកាចាប់ម្តើេម្េើចំណណកទី២ភ្លាេ
• ប្បូផាសII


  1. ត្តយ ៉ូងអាត្ក៉ូម ាទិចមកើតមាៃកនុងមកាសិកាក៉ូៃៃីេួយៗ

  2. ត្ក៉ូេ ៉ូស៉ូេណដលមត្បោះតាេបម្តាយ ម្េើដំមណើរមឆ្ពាោះម ាណ្នកក្តាលនៃត្តយ ៉ូងអាត្ក៉ូម ាទិច
• ហេតាផាសII


  • ត្ក៉ូេ ៉ូស៉ូេមត្បោះតាេបម្តាយ ភ្ជាប់ខ្លួៃម ាៃឹងត្តយ ៉ូងអាត្ក៉ូម ាទិច ម ាយសង់ត្ត៉ូណេ
  • ត្ក៉ូេ ៉ូស៉ូេទាំងអស់ ត្បេ៉ូល្តុំគ្នាម ាមលើបលង់មអកេាទ័ររបស់មកាសិកា
• អាណាផាសII

  1. សង់ត្ត៉ូណេរម្េើចំណណកណដលន្ាំឱ្យត្ក៉ូម ាទីតបងបអូៃ ាច់មចញពីគ្នា

  2. ដ៉ូចមៃោះត្ក៉ូម ាទីតៃីេួយៗកលាយជាត្ក៉ូេ ៉ូស៉ូេក៉ូៃ

  3. បន្ទាប់េកត្ក៉ូេ ៉ូស៉ូេក៉ូៃទាំងពីរម្េើដំមណើរមឆ្ពាោះម ាកាៃ់ប ៉ូល២ ្ទុយគ្នារបស់ត្តយ ៉ូងអាត្ក៉ូម ាទិច
• ហ ឡូផាសII

  1. ត្កុេត្ក៉ូេ ៉ូស៉ូេៃីេួយៗបាៃេកដល់ប ៉ូល

  2. ភ្នាសនណេយ ៉ូមកើតម ើង

  3. ត្តយ ៉ូងអាត្ក៉ូម ាទិចក៏រលាយបាត់

  4. បន្ទាប់េកសុីត៉ូបលាសម្េើចំណណកបាៃជាមកាសិកាក៉ូៃ២

  5. ម ាចុងបញ្ចប់នៃចំណណកទី២ របស់មេយ ៉ូសមកាសិកាឌីបលូអ ៊ីតេួយបមងកើតបាៃមកាសិកាក៉ូៃអាបលូអ ៊ីត៤
• Crossing over


  A process that occurs during prophase I of meiosis, where homologous chromosomes exchange genetic material through the breaking and rejoining of DNA strands, resulting in new combinations of genetic material on each homologous chromosome.
• Homologous chromosomes


  Chromosomes that have the same genes in the same order, but may have different alleles. They pair up and exchange genetic material during crossing over in meiosis.
• Meiosis


  A type of cell division that results in the formation of haploid cells (gametes) from a diploid cell (parent cell). It involves two main stages: meiosis I and meiosis II.
• Meiosis II


  The second stage of meiosis, where each haploid daughter cell from meiosis I divides again to form two more haploid daughter cells, resulting in a total of four haploid cells.
• Meiosis I


  The first stage of meiosis, where a diploid cell divides into two haploid daughter cells through a series of steps: prophase I, metaphase I, anaphase I, and telophase I.