Cell cycle & cell division.htm
- 1. Cellular Division Unicellular: for reproduction Multicellular: growth/repair of damaged body parts Renewal/repair of worn out cells 1
- 2. Words to know • DNA/RNA • Chromosomes - organized structure of DNA and protein • Chromatins - mass of genetic material composed of DNA and proteins that condense to form chromosomes during eukaryotic cell division • Chromatids - each of the two threadlike strands into which a chromosome divides longitudinally during cell division. Each contains a double helix of DNA. 2
- 3. Cell Division All cells are derived from pre- existing cells New cells are produced for growth and to replace damaged or old cells Allows the cell to pass DNA copy to daughter cells Differs in prokaryotes (bacteria) and eukaryotes (protists, fungi, plants, & animals) 3
- 4. Keeping Cells Identical The instructions for making cell parts are encoded in the DNA, so each new cell must get a complete set of the DNA molecules 4
- 5. DNA Replication DNA must be copied or Original DNA strand replicated before cell division Two new, identical DNA Each new cell strands will then have an identical copy of the DNA 5
- 6. Identical Daughter Cells Two identical daughter cells Parent Cell 6
- 7. Chromosomes structure within the cell that bears the genetic or as a circular material as a threadlike strand of DNA (or linear strand of DNA RNA in some bonded to various viruses) in the proteins in the nucleus cytoplasm of of eukaryotic cells prokaryotes 7
- 8. Prokaryotic Chromosome The DNA of prokaryotes (bacteria) is one, circular chromosome attached to the inside of the cell membrane 8
- 9. Eukaryotic Chromosomes All eukaryotic cells store genetic information in chromosomes Most eukaryotes have between 10 and 50 chromosomes in their body cells Human body cells have 46 chromosomes or 23 identical pairs 9
- 10. Eukaryotic Chromosomes Each chromosome is composed of a single, tightly coiled DNA molecule Chromosomes can’t be seen (with a microscope) when cells aren’t dividing and are called chromatin 10
- 11. Compacting DNA into Chromosomes DNA is tightly coiled around proteins called histones 11
- 12. Chromosomes in Dividing Cells Duplicated chromosomes are called chromatids & are held together by the centromere Called Sister Chromatids 12
- 13. Karyotype A picture of the chromosomes from a human cell arranged in pairs by size First 22 pairs are called autosomes Last pair are the sex chromosomes XX female or XY male 13
- 14. Boy or Girl? The Y Chromosome Decides Y - Chromosome X - Chromosome 14
- 15. Cell Reproduction 15
- 16. Types of Cell Reproduction Asexual reproduction involves a single cell dividing to make 2 new, identical daughter cells Mitosis & binary fission are examples of asexual reproduction Sexual reproduction involves two cells (egg & sperm) joining to make a new cell (zygote) that is NOT identical to the original cells Meiosis is an example 16
- 17. Division Mechanisms Prokaryotic organisms – Binary fission Eukaryotic organisms – Mitosis • Karyokinesis (division of nucleus) • Cytokinesis (division of cytoplasm) – Meiosis
- 18. Cell Division in Prokaryotes 18
- 19. Cell Division in Prokaryotes Prokaryotes such as Parent bacteria divide into 2 cell identical cells by the process of binary fission Chromosome Single chromosome doubles makes a copy of itself Cell splits Cell wall forms between the chromosomes dividing the cell 2 identical daughter cells 19
- 20. Prokaryotic Cell Undergoing Binary Fission 20
- 21. Animation of Binary Fission 21
- 22. The Cell Cycle 22
- 23. Five Phases of the Cell Cycle G1 - primary growth/gap phase S – synthesis; DNA replicated G2 - secondary growth/gap phase collectively these 3 stages are called interphase M - mitosis C - cytokinesis 23
- 24. Cell Cycle 24
- 25. Interphase - G1 Stage 1st growth/gap stage after cell division Cells mature by making more cytoplasm & organelles Cell carries on its normal metabolic activities i.e. respiration, digestion etc. 25
- 26. Interphase – S Stage Synthesis stage DNA is copied or replicated Two identical copies of DNA Original DNA 26
- 27. Interphase – G2 Stage 2nd Growth/Gap Stage Occurs after DNA has been copie; also in preparation for M phase All cell structures needed for division are made (e.g. centrioles) Both organelles & proteins are synthesized 27
- 28. What’s Happening in Interphase? What the cell looks like Animal Cell What’s occurring 28
- 29. Sketch the Cell Cycle DNA Copied Cells prepare for Cells Division Mature Daughter Cells Cell Divides into Identical cells 29
- 30. Mitosis 30
- 31. Mitosis Division of the nucleus (karyokinesis) Division of the cytoplasm (cytokinesis) Only occurs in eukaryotes Has four stages Doesn’t occur in some cells such as brain cells 31
- 33. Early Prophase Chromatin in nucleus condenses to form visible chromosomes Mitotic spindle forms from fibers in cytoskeleton or centrioles (animal) Nucleolus Cytoplasm Nuclear Membrane Chromosomes 33
- 34. Late Prophase Nuclear membrane & nucleolus are broken down Chromosomes continue condensing & are clearly visible Spindle fibers called kinetochores attach to the centromere of each chromosome Spindle finishes forming between the poles of the cell 34
- 35. Late Prophase Chromosomes Nucleus & Nucleolus have disintegrated 35
- 36. Spindle Fiber attached to Chromosome Kinetochore Fiber Chromosome 36
- 37. Review of Prophase What the cell looks like What’s happening 37
- 38. Spindle Fibers The mitotic spindle form from the microtubules in plants and centrioles in animal cells Polar fibers extend from one pole of the cell to the opposite pole Kinetochore fibers extend from the pole to the centromere of the chromosome to which they attach Asters are short fibers radiating from centrioles 38
- 39. Sketch The Spindle 39
- 40. Metaphase Chromosomes, attached to the kinetochore fibers, move to the center of the cell Chromosomes are now lined up at the equator Equator of Cell Pole of the Cell 40
- 41. Metaphase Asters at the poles Spindle Chromosomes Fibers lined at the Equator 41
- 42. Metaphase Aster Chromosomes at Equator 42
- 43. Review of Metaphase What the cell looks like What’s occurring 43
- 44. Anaphase Occurs rapidly Sister chromatids are pulled apart to opposite poles of the cell by kinetochore fibers 44
- 45. Anaphase Sister Chromatids being separated 45
- 46. Anaphase Review What the cell looks like What’s occurring 46
- 47. Telophase Sister chromatids at opposite poles Spindle disassembles Nuclear envelope forms around each set of sister chromatids Nucleolus reappears CYTOKINESIS occurs Chromosomes reappear as chromatin 47
- 48. Comparison of Anaphase & Telophase 48
- 49. Cytokinesis Means division of the cytoplasm Division of cell into two, identical halves called daughter cells In plant cells, cell plate forms at the equator to divide cell In animal cells, cleavage furrow forms to split cell 49
- 50. Cytokinesis Cleavage furrow Cell plate in in animal cell animal cell 50
- 51. Mitotic Stages 51
- 52. Daughter Cells of Mitosis Have the same number of chromosomes as each other and as the parent cell from which they were formed Identical to each other, but smaller than parent cell Must grow in size to become mature cells (G1 of Interphase) 52
- 53. Identical Daughter Cells What is the 2n or diploid number? 2 Chromosome number the same, but cells smaller than parent cell 53
- 54. Review of Mitosis 54
- 55. Draw & Learn these Stages 55
- 56. Draw & Learn these Stages 56
- 57. Name the Mitotic Stages: Interphase Name this? Prophase Telophase Name this? Metaphase Anaphase 57
- 58. Eukaryotic Cell Division Used for growth and repair Produce two new cells identical to the original cell Chromosomes during Metaphase of mitosis Cells are diploid (2n) Prophase Metaphase Anaphase Telophase Cytokinesis 58
- 59. Mitosis Animation Name each stage as you see it occur? 59
- 60. Mitosis in Onion Root Tips Do you see any stages of mitosis? 60
- 61. Test Yourself over Mitosis 61
- 62. Mitosis Quiz 62
- 63. Mitosis Quiz 63
- 64. Name the Stages of Mitosis: Early prophase Early Anaphase Metaphase Interphase Early Telophase, Begin cytokinesis Late Late telophase, Prophase Advanced Mid-Prophase Late cytokinesis Anaphase 64
- 65. Identify the Stages ? Early, Middle, & Late Prophase ? ? ? Metaphase Anaphase Late Prophase ? ? ? Late Anaphase Telophase Telophase & Cytokinesis 65
- 66. Locate the Four Mitotic Stages in Plants Anaphase Telophase Metaphase Prophase 66
- 67. Uncontrolled Mitosis If mitosis is not controlled, unlimited cell division occurs causing cancerous tumors Oncogenes are special proteins that increase the chance that a normal cell develops into a tumor cell Cancer cells 67
- 68. Meiosis Formation of Gametes (Eggs & Sperm) 68
- 69. Words to know Gametes - reproductive cells that unite during sexual reproduction to form a new cell called a zygote (male = sperm, female = egg cell) Germ cells – sperm or egg cells Somatic cells - any cell other than the reproductive cells Diploid - a cell that contains two sets of chromosomes (2n), as normally found in somatic cells Haploid - have one set of chromosomes (n=1) as in germ cells, or half as many as a somatic cell Homologous – chromosomes that are alike in structure and genes Alleles – different forms of a gene ex. if talking about hair color as the gene, different alleles would be different colors like red, blonde, black etc. 69
- 70. Facts About Meiosis Preceded by interphase which includes chromosome replication Two meiotic divisions: Meiosis I and Meiosis II Aka reduction-division Original cell is diploid (2n) Four daughter cells produced that are haploid (n) 70
- 71. Facts About Meiosis Daughter cells contain half the number of chromosomes as the original cell Produces gametes (eggs & sperm) Occurs in the testes in males (Spermatogenesis) Occurs in the ovaries in females (Oogenesis) Human diploid cells have 46 chromosomes (2n=46) Human sperm and egg cells have 23 chromosomes (n=23) each 71
- 72. More Meiosis Facts Start with 46 double stranded chromosomes (2n) After 1 division - 23 double stranded chromosomes (n) After 2nd division - 23 single stranded chromosomes (n) Occurs in our germ cells 72
- 73. Why Do we Need Meiosis? It is the fundamental basis of sexual reproduction Two haploid (1n) gametes are brought together through fertilization to form a diploid (2n) zygote 73
- 74. Fertilization – “Putting it all together” 2n = 6 1n =3 74
- 75. Replication of Chromosomes Replication is the process of duplicating a Occurs in chromosome Interphase Occurs prior to division Replicated copies are called sister chromatids Held together at centromere 75
- 76. A Replicated Chromosome Gene X Homologues Sister (same genes, Chromatids different alleles) (same genes, same alleles) Homologues separate in meiosis I and therefore different alleles separate. 76
- 77. Meiosis Forms Haploid Gametes Meiosis must reduce the chromosome number by half Fertilization then restores the 2n number from mom from dad child too much! meiosis reduces genetic content The right number! 77
- 78. Meiosis: Two Part Cell Division Sister chromatids Homologues separate separate Meiosis Meiosis I II Diploid Diploid Haploid 78
- 79. Meiosis I: Reduction Division Nucleus Spindle fibers Nuclear Early envelope Prophase I Late Metaphase (Chromosome Prophase I Anaphase Telophase I number I I (diploid) doubled) 79
- 80. Prophase I Early prophase Late prophase Homologues Chromosomes condense. pair. Spindle forms. Crossing over Nuclear envelope occurs. fragments. 80
- 81. Tetrads Form in Prophase I Homologous chromosomes Join to form a (each with sister chromatids) TETRAD Called Synapsis 81
- 82. Crossing-Over Homologous chromosomes in a tetrad cross over each other Pieces of chromosomes or genes are •Occurs in nonsister chromatids exchanged •Increases genetic variability Produces Genetic recombination in the offspring Genetic recombination in which a strand of the genetic material (DNA/RNA)is broken and then joined to the end of a different DNA molecule. 82
- 83. Homologous Chromosomes During Crossing-Over 83
- 84. Crossing-Over Crossing-over multiplies the already huge number of different gamete types produced by independent assortment 84
- 85. Metaphase I Homologous pairs of chromosomes align along the equator of the cell 85
- 86. Anaphase I Homologues separate and move to opposite poles. Sister chromatids remain attached at their centromeres. 86
- 87. Telophase I Nuclear envelopes reassemble. Spindle disappears. Cytokinesis divides cell into two. 87
- 88. Meiosis II Only one homologue of each Gene X chromosome is present in the cell. cell Sister chromatids carry identical genetic information. Meiosis II produces gametes with one copy of each chromosome and thus one copy of each gene. 88
- 89. Meiosis II: Reducing Chromosome Number Prophase Metaphase II Telophase II Anaphase II 4 Identical II haploid cells 89
- 90. Prophase II Nuclear envelope fragments. Spindle forms. 90
- 91. Metaphase II Chromosomes align along equator of cell. 91
- 92. Anaphase II Equator Pole Sister chromatids separate and move to opposite poles. 92
- 93. Telophase II Nuclear envelope assembles. Chromosomes decondense. Spindle disappears. Cytokinesis divides cell into two. 93
- 94. Results of Meiosis 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 94
- 95. Gametogenesis Oogenesis or Spermatogenesis 95
- 96. Spermatogenesis Occurs in the testes Two divisions produce 4 spermatids Spermatids mature into sperm Men produce about 250,000,000 sperm per day 96
- 97. Spermatogenesis in the Testes Spermatid 97
- 98. Spermatogenesis 98
- 99. Oogenesis Occurs in the ovaries Two divisions produce 3 polar bodies that die and 1 egg Polar bodies die because of unequal division of cytoplasm Immature egg called oocyte Starting at puberty, one oocyte matures into an ovum (egg) every 28 days 99
- 100. Oogenesis in the Ovaries 100
- 101. Oogenesis First polar body may divide a (haploid) X a Polar bodies a X die a X X Mitosis Meiosis I Meiosis II A X (if fertilization Oogonium occurs) A (diploid) Primary X oocyte (diploid) A X Ovum (egg) Mature Secondary A egg oocyte X (haploid) Second polar body (haploid) 101
- 102. Comparing Mitosis and Meiosis 102
- 103. Comparison of Divisions Mitosis Meiosis Number of 2 1 divisions Number of 2 4 daughter cells Genetically Yes No identical? Chromosome # Same as parent Half of parent Where Somatic cells Reproductive cells When Throughout life At sexual maturity Growth and Role Sexual reproduction repair 103
- 104. Meiosis Mitosis A type of cellular reproduction in A process of asexual reproduction which the number of chromosomes in which the cell divides in two Definition: are reduced by half through the producing a replica, with an equal separation of homologous number of chromosomes in haploid chromosomes in a diploid cell. cell Cellular Reproduction & general Function: sexual reproduction growth and repair of the body Type of Reproduction: Sexual Asexual Occurs in: Humans, animals, plants, fungi all organisms Genetically: different identical Yes, mixing of chromosomes can Crossing Over: No, crossing over cannot occur. occur. Pairing of Homologues: Yes No Number of Divisions: 2 1 Number of Haploid Daughter Cells 4 2 produced: Chromosome Number: Reduced by half Remains the same The steps of meiosis are The steps of mitosis are Interphase, Prophase I, Metaphase Interphase, Prophase, Metaphase, Steps: I, Anaphase I, Telophase I, Anaphase, Telophase and Prophase II, Metaphase II, Cytokinesis Anaphase II and Telophase II. Karyokenesis: Occurs in Interphase I Occurs in Interphase Occurs in Telophase I & Telohpase Cytokenesis: Occurs in Telophase II The centromeres do not separate The centromeres split during Centromeres Split: during anaphase I, but during Anaphase anaphase II Sex cells only: Female egg cells or Makes everything other than sex Creates: 104
- 105. Quiz #1 1. The stage of the cell cycle where each chromosome is composed of 2 chromatids in preparation for mitosis. a. G1 c. M b. S d. G2 2. Which of the following distinguishes prophase I of meiosis from prophase of mitosis? a. Homologue chromosomes pair up b. Spindle forms c. nuclear membrane breaks down d. chromosomes become visible 105
- 106. 3. Which sequence of the cell cycle is common to eukaryotes? a. G1, G2, S, M, cytokinesis b. G1, M, G2, S, cytokinesis c. G1, S, M, G2, cytokinesis d. G1, S, G2, M, cytokinesis 4. A cell with forty two chromosomes divides mitotically. How many chromosomes will each gamete have? a. 21 c. 84 b. 42 d. 168 106
- 107. 5. If given the allele brown, which among the genes below is it NOT an alternative form of? a. Hair color c. Nail color b. Skin color d. Eye color 6. Meiosis results in: a. 2 haploid daughter cells b. 4 haploid daughter cells c. 2 diploid daughter cells d. 4 diploid daughter cells 107
- 108. 7. Which of the following cells undergo meiosis? a. Sperm cells c. Brain cells b. Kidney cells d. All of the above 8. Which refers to the region of attachment for two sister chromatids? a. Centriole c. Microtubule b. Cenromere d. Spindle fiber 108
- 109. 9. How many chromosomes are there in a mature human cell? a. No chromosomes b. 26 pairs of chromosomes c. 44 chromosomes and X and Y chromosomes d. 50 chromosomes 10. Cytokinesis occurs during which phase of meiosis? a. Telophase c. Prophase b. Anaphase d. Metaphase 109
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Editor's Notes
- #76: Replication is the process of duplicating chromosome. The new copy of a chromosome is formed by DNA synthesis during S-phase. The chromosome copies are called sister chromatids. Sister chromatids are held together at the centromere.