Cellular Reproduction

Cellular Reproduction
Prokaryotic cell division
Eukaryotic cell division
Mitosis
Meiosis

1. CELLULAR REPRODUCTION Dr. PULIPATI SOWJANYA Professor & Head Dept. of Pharm. Biotechnology VIGNAN PHARMACY COLLEGE Vadlamudi – 522 213, Guntur ( Dt ), Andhra Pradesh, INDIA 1 PRESENTED BY

2. CELLULAR REPRODUCTION Cells reproduce by dividing into two in the process called cell division  Each dividing cell is called mother cell or parent cell, and its descendants are called daughter cells  The parent cell transmits copies of its hereditary information (DNA) to its daughter cells which in turn, pass it to their own daughter cells, becoming yet another parent cell, and so on and so forth 2 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt )

3. CELLULAR REPRODUCTION As a cell prepares to divide, the DNA inside the nucleus becomes organized into chromosomes This is to ensure that both of the new cells get all of the genetic information from the original cell 3 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt )

4. Chromosome Structure Chromosomes are rod shaped structures made of DNA and proteins found in the nucleus of cells 4 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt )

5. Chromosome Structure Chromosomes consist of 2 identical halves called chromatids – When a cell divides, each of the two new cells will receive one chromatid • Two chromatids are attached at the centromere Between cell divisions, DNA is not so tightly coiled • This form is called chromatin 5 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt )

6. Chromosome Numbers Animal chromosomes are categorized as either sex chromosomes or autosomes – Sex chromosomes determine the sex of an organism • In humans, sex chromosomes are X or Y (females = XX, males = XY) – All of the other chromosomes are autosomes Every cell of an organism produced by sexual reproduction has two copies of each autosome (one from each parent) • The two copies are called homologous chromosomes – Same size and shape and carry genes for the same traits 6 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt )

7. Diploid and Haploid Cells Diploid – cells that have 2 sets of chromosomes (46 total in humans) Haploid – cells that only have 1 set of chromosomes (23 total in humans) • Only sperm and egg cells are haploid 7 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt )

8. CELLULAR DIVISION Cell division is often referred to as cellular reproduction  Most prokaryotic cells, by simply separating the contents of the cell into two parts  Eukaryotic cells can divide either through a process called mitosis or meiosis. 8 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt )

9. CELLULAR DIVISION IN PROKARYOTES Binary fission is the division of a prokaryotic cell into two offspring cells 9 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt )

10. CELLULAR DIVISION IN EUKARYOTES Two types of cell division – Mitosis results in new cells that are identical to the original cell – Meiosis occurs during the formation of gametes (haploid reproductive cells) 10 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt )

11. CELL CYCLE A repeating set of events in the life of a cell • Division is one phase of the cycle • Time between cell divisions is called interphase 11 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt )

12. Interphase 1. G1 phase – offspring cells grow to mature size 2. S phase – the cell’s DNA is copied 3. G2 phase – cell prepares for cell division • Cells can exit the cycle and enter into the G0 phase to stop dividing (ex: fully developed brain cells) 12 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt )

13. Stages of Mitosis 13 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt )

14. Prophase 14 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) Prophase (Gk. Pro – before or first, phasis – appearance or stage DNA condenses into chromosomes • Nuclear membrane breaks down • Centrosomes form and microtubules grow from them (called the mitotic spindle)

15. Metaphase 15 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) Metaphase (Gk. Meta – after or second, phasis – stage) Chromosomes line up in the middle of the cell • Spindle fibers attach to the centromere of each chromosome

16. Anaphase 16 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) Anaphase: (Gk. Ana – up, phasis – appearance or stage) Chromatids are pulled apart and move to opposite ends of the cell. It lasts only for few minutes

17. Telophase 17 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) Telophase : (Gk. Telos – end, phasis – appearance or stage Chromosomes reach opposite ends of the cell • Spindle fibers disassemble • Chromosomes unravel • Nuclear membranes reform

18. Significance of Mitosis 18 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) Surface to Volume Ratio: Increase in cell size reduces surface area to volume ratio and decreases efficiency in exchange of materials. Nucleo-cytoplasmic Ratio: Nucleus controls all metabolic activities occuring in the cytoplasm. Increased volume of cytoplasm due to cell growth reduces the nucleo-cytoplasmic ratio. Equitable distribution of genetic material: Qualitative and quantitative equitable distribution of chromosomes in all the body cells of an organism by mitotic divisions maintains similar genetic constitution in them.

19. Significance of Mitosis 19 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) Growth of Multicellular Organisms: It occurs due to increase in number of cells rather than increase in cell size because smaller cells are more efficient. Asexual Reproduction: It helps in vegetative propagation of plants and asexual reproduction in lower organisms. Unicellular organisms multiply by this method. Healing of wounds: Mitotic divisions in healthy cells surrounding the area of injury help in healing the wounds. Regeneration: The lost organs in plants and animals like earthworm, tail of lizard can be regenerated by mitosis.

20. Control of Cell Division 20 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) A cell spends most of its time in interphase • What tells the cells to exit interphase and begin dividing? • There are three main checkpoints that act as “traffic signals” for the cell to divide or not to divide

21. Control of Cell Division 21 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) 1. Cell growth (G1) checkpoint – controls whether the cell will divide 2. DNA synthesis (G2) checkpoint – make sure DNA was copied properly 3. Mitosis checkpoint – signals tell the cell to exit mitosis

22. What Happens When Control Is Lost 22 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) • If a mutation occurs in one of the genes that regulates the cell cycle, cell growth and division could be disrupted • This disruption could lead to cancer – the uncontrolled growth of cells

23. MITOSIS Vignan Pharmacy College, Vadlamudi, Guntur (Dt) 23 https://www.youtube.com/watch?v=DwAFZb8juMQ

24. Meiosis 24 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) • A process of nuclear division that reduces the number of chromosomes in new cells to half the number in the original cell

25. Formation of Haploid Cells 25 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) • Meiosis produces gametes, which are haploid reproductive cells • Cells preparing to divide by meiosis undergo the G1, S, and G2 phases of interphase – Cells begin meiosis with a duplicate set of chromosomes, just like mitosis • Cells undergoing meiosis divide twice, resulting in 4 haploid (1n) cells

26. Two Stages of Meiosis 26 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) • First cell division = Meiosis I – Prophase I, Metaphase I, Anaphase I, Telophase I and Cytokinesis I • Second cell division = Meiosis II – Prophase II, Metaphase II, Anaphase II, Telophase II and Cytokinesis II

27. Meiosis I 27 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt )

28. Meiosis II 28 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt )

29. Prophase I 29 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) • DNA coils tightly into chromosomes • Spindle fibers appear • Nuclear membrane is assembles • Synapsis occurs - homologous chromosomes line up next to each other – Each pair is called a tetrad

30. Prophase I 30 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) • Crossing-over occurs – portions of chromatids may break off and attach to adjacent chromatids • Genetic recombination results – genetic material between maternal and paternal chromosomes is exchanged

31. Metaphase I 31 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) • Tetrads line up along the middle of the cell • Spindle fibers attach to the centromere of each homologous chromosome

32. Anaphase I 32 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) • Each homologous chromosome moves to an opposite end of the cell • Random separation of homologous chromosomes is called independent assortment and results in genetic variation

33. Telophase I and Cytokinesis I 33 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) • Chromosomes reach opposite ends of thecell and cytokinesis begins • Two new cells areproduced , each containing onechromosome from each homologous pair (haploid – 1n)

34. Prophase II 34 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) • Spindle fibers form and begin to move the chromosomes toward the midline of the dividing cell

35. Metaphase II 35 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) • Chromosomes move to the midline of the dividing cell

36. Anaphase II 36 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) • Chromatids separate and move toward opposite ends of the cell

37. Telophase II and Cytokinesis II 37 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) • Telophase II – nuclear membrane forms around the chromosomes in each of the four new cells • Cytokinesis II – 4 new cells are formed, each with half of the original cell’s number of chromosomes

38. Telophase II and Cytokinesis II 38 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) • Telophase II – nuclear membrane forms around the chromosomes in each of the four new cells • Cytokinesis II – 4 new cells are formed, each with half of the original cell’s number of chromosomes

39. Differences Between Mitosis and Meiosis 39 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) MITOSIS  Occurs in somatic or body cells  Direct cellular division  Produce two diploid daughter cells  The daughter cells are exactly alike MEIOSIS  Occurs in reproductive cells or gametes  Has two successive division (meiosis I and meiosis II)  Produce four haploid daughter cells  The daughter cells are not all alike

40. MEIOSIS Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) 40 https://www.youtube.com/watch?v=-Lx0oLPnRQg&t=81s

41. Results of Meiosis 41 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) Gametes (egg & sperm) form Four haploid cells with one copy of each chromosome One allele of each gene Different combinations of alleles for different genes along the chromosome

42. Development of Gametes 42 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) • In animals, the only cells that divide by meiosis are those that produce gametes within the reproductive organs – In humans – testes (males) and ovaries (females)

43. Development of Gametes 43 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) SPERMATOGENESIS • In the testes – male gametes known as sperm cells or spermatozoa are produced • One diploid cell divides meiotically to form four haploid cells called spermatids – each develops into a mature sperm cells

44. Development of Gametes 44 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) OOGENESIS • Production of mature egg cells, or ova • A diploid reproductive cell divides meiotically to produce one mature egg cell (ovum) and three polar bodies which will degenerate – cytoplasm is not evenly distributed in cytokinesis

45. Sexual Reproduction 45 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) • Production of offspring through meiosis and the union of a sperm and an egg • Offspring are genetically different because genes are combined in new ways • Advantage: enables species to adapt rapidly to new conditions

46. Significance of Meiosis 46 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) Sexual Reproduction: Meiosis and fertilization are essential in the life cycle of sexually reproducing organisms. Maintenance of Chromosome Number: Fertilization of haploid gametes doubles the chromosome number in the zygote. Meiosis halves the chromosome number during different stages of life cycle. Thus, it helps in maintaining the same chromosome number in a species. Segregation of Alleles: Meiosis helps in segregation of alleles of different characters due to disjunction of homologous chromosomes of each bivalent in meiosis-I.

47. Significance of Meiosis 47 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) Crossing over: Crossing over between non-sister chromatids of paternal and maternal homologous chromosomes of each bivalent during prophase-I of meiosis helps in recombination of linked genes. Gene Mutations: The chances of gene mutations increase during meiosis due to breakage and reunion of DNA molecules during crossing over. Mutations are fountain head of all variations. Evolution: Variations produced during meiosis from the basis of evolution due to natural selection of better recombinants.

48. Pharmaceutical Applications of Cell Reproduction 48 Vignan Pharmacy College, Vadlamudi, Guntur ( Dt ) The cell cycle is regulated to fit the needs of the organism. Important discoveries in the last decade helped to understand the regulation of cell cycle and how abnormalities in cell cycle regulation contribute to the development of cancer. Gene therapy technique to repair the genetic defects that cause cancer.

49. THANK YOU 49