05 cell division
- 2. CELL DIVISION Why do cells need to divide? To allow an organism to grow To pass on genetic material To assist an organism’ survival
- 3. CELL DIVISION 2 types of cell division Mitosis -daughter cells are genetically identical Meiosis -daughter cells are genetically different
- 4. CELL DIVISION Mitosis Literally refers to the division of the nucleus 5 stages : Interphase Prophase Metaphase Anaphase Telophase
- 5. CELL DIVISION Interphase Cell is not dividing but also not dormant Cell is active and growing and also preparing for division Sometimes called resting phase but this is inaccurate (real resting phase is G 0 ) DNA/chromosomes not visible (unwound)
- 6. CELL DIVISION Interphase: 4 stages Gap 0 (G 0 ): - Cell rest cycle - may be temporary or permanent (where cells are functional but no new cells are produced (i.e. neuron) G 0
- 7. CELL DIVISION Interphase: 4 stages Gap 1 (G 1 ): - Rapid growth (4hr) - cell takes in nutrients for energy, growth, repair - Cells either go into S or G 0 after G1 G 0
- 8. CELL DIVISION Interphase: 4 stages S phase (S): - 10 hrs - DNA synthesis/ replication - the cell duplicates its genetic material to make an identical copy of its DNA G 0
- 9. CELL DIVISION Interphase: 4 stages Gap 2 phase (G 2 ): - 3-4hr - second period of growth in preparation for cell division -cell grows larger in size G 0
- 10. CELL DIVISION S phase (S): Let’s take a closer look - the cell duplicates its DNA - what is DNA? Deoxyribose nucleic acid - Contains genetic information in coded form
- 11. CELL DIVISION S phase (S): Let’s take a closer look Deoxyribose nucleic acid Made of: Sugar (deoxyribose) Phosphate (PO 4 ) Nucleotide base
- 12. CELL DIVISION S phase (S): Let’s take a closer look Nucleotide bases enable the coding of genetic information A – adenine T – Thymine G – Guanine C – Cytosine
- 13. CELL DIVISION S phase (S): Let’s take a closer look The “coded” information is a sequence of nucleotide bases A – adenine T – Thymine G – Guanine C – Cytosine Every 3 nucleotide bases code for 1 specific amino acid (so every 3 bases, called a codon , is one instruction)
- 14. CELL DIVISION S phase (S): Let’s take a closer look 3 nucleotide bases code for 1 amino acid This is the genetic language For example, A C G makes Threonine
- 15. CELL DIVISION S phase (S): Let’s take a closer look A attracts T G attracts C The bases attract through HYDROGEN BONDING and fit together like Lego pieces This is called complimentary base pairing.
- 16. CELL DIVISION S phase (S): Let’s take a closer look Adenine & Guanine are purines ( 2-ring nitrogenous bases) Thymine & Cytosine are pyrimidines ( 1-ring nitrogenous bases)
- 17. CELL DIVISION S phase (S): Let’s take a closer look A and T: bond together with 2 hydrogen bonds C and G: bond together with 3 hydrogen bonds
- 18. CELL DIVISION S phase (S): Let’s take a closer look Which ones are A&T? Which ones are C&G? A&T A&T C&G C&G
- 19. CELL DIVISION S phase (S): Let’s take a closer look How does DNA replicate? STEP 1: Separation of the two DNA strands
- 20. CELL DIVISION S phase (S): Let’s take a closer look How does DNA replicate? STEP 2: Each “parental strand” now attracts respective nucleotide bases to form a new chain New chain Nucleotide bases
- 21. CELL DIVISION S phase (S): Let’s take a closer look How does DNA replicate? STEP 3: The nucleotides are connected to form a sugar-phosphate backbone
- 22. CELL DIVISION S phase (S): Let’s take a closer look How does DNA replicate? But DNA is a very long molecule. Does replication start from one end? Not usually. It can start at various points in “bubbles”
- 23. CELL DIVISION S phase (S): Let’s take a closer look How does DNA replicate? 3 models of replication
- 24. CELL DIVISION S phase (S): Let’s take a closer look … Back to interphase where DNA duplication occurs. Normally After duplication DNA duplication
- 25. CELL DIVISION How does all of the DNA remain organized in the nucleus? Why does it not tangle?
- 26. CELL DIVISION DNA strands are wrapped around histone proteins which act as “ spools ”
- 27. CELL DIVISION Histone proteins that have been wrapped with DNA form “ nucleosomes ”
- 28. CELL DIVISION Moving into mitosis… After interphase, the cell may enter mitotic (M) phase: A process by which somatic cells grow and divide Cells come from pre-existing cells Parent cell divides to produce two new identical daughter cells Cell division occurs through: A) Mitosis – process of dividing nuclear material B) Cytokinesis – Process of separating the cytoplasm and its contents into equal parts
- 29. CELL DIVISION Prophase nuclear membrane breaks down chromosomes shorten and thicken Other structures important for mitosis are also forming (i.e. the centrioles )
- 30. CELL DIVISION Prophase chromosomes shorten and thicken into X-shaped things
- 31. CELL DIVISION Prophase A centromere holds two copies of the same chromosome together Each copy of a chromosome is called a chromatid
- 32. CELL DIVISION Prophase A centromere holds two copies of the same chromosome together Remember, every chromosome has been duplicated during the S phase of interphase . Recall this: 2 copies of each chromosome: Mitosis Colors are not accurate Father’s side Mother’s side Father’s side Father’s side Mother’s side Mother’s side
- 34. CELL DIVISION Metaphase Proteins attach to the centromeres creating the kinetochores . Microtubules (spindle fibres) attach at the kinetochores and the chromosomes move to the centre ( the metaphase plate )
- 36. CELL DIVISION Anaphase Paired chromosomes separate at the kinetochores and move to opposite sides of the cell Motion results from kinetochore movement along the spindle microtubules
- 37. CELL DIVISION Telophase Chromatids arrive at opposite poles of cell New membranes form around the daughter nuclei Chromosomes disperse and are no longer visible under the light microscope spindle fibres disperse
- 38. CELL DIVISION Cytokinesis Animal cells: the cell membrane pinches (forming a cleavage furrow ) into two daughter cells, each with one nucleus
- 39. CELL DIVISION Cytokinesis In plant cells, a cell plate (made of rigid cellulose) is synthesized between the two daughter cells.
- 40. CELL DIVISION Mitosis and cytokinesis: Review
- 41. CELL DIVISION Mitosis and cytokinesis: Haploid and Diploid Haploid = 1 set of chromosomes (ex. n=23 chromosomes) Diploid = 2 sets of chromosomes (ex. 2n= 46 chromosomes) 2n 4n 4n 2n 2n
- 42. CELL DIVISION Karyotype: Photograph of chromosomes taken at the metaphase stage of mitosis. Homologous pairs are identified and placed together. Homologous pair daddy mommy
- 43. CELL DIVISION Karyotype: Technique Pretreat cells with a hypotonic solution, which swells them and spreads the chromosomes stop mitosis in metaphase by a solution of colchicine 3) Compressing the preparation on a slide, forcing the chromosomes into a single plane 4) Taking a high resolution photograph 5) Cutting up a photomicrograph and arranging the result into an indisputable karyogram
- 44. CELL DIVISION Karyotype: Technique But during mitosis, chromosomes are in DUPLICATED pairs. So each homologous pair consists of 2 X-shaped chromosomes Scientists can cut the photographs so that only one chromatid of every chromosome is displayed
- 45. CELL DIVISION Homologous pairs Identified by -chromosome length -centromere position -banding pattern -satellite endings and any other physical characteristics
- 46. CELL DIVISION Recall: 2 types of cell division Mitosis -daughter cells are genetically identical Meiosis -daughter cells are genetically different
- 47. CELL DIVISION Meiosis: The division of gametes 2 cell divisions (meiosis I and meiosis II) Daughter cells are genetically unique 4 daughter cells are produced Daughter cells are haploid
- 48. CELL DIVISION Meiosis I: Prophase I -start with 2x the normal amount of chromosomes -chromosomes condense -nuclear membrane dissolves -centrioles split -chromosomes come together in homologous pairs, forming tetrads -they overlap in a process called synapsis - crossover of chromatids causing exchange of segments of DNA Same as mitosis
- 49. CELL DIVISION Meiosis I: Prophase I -chromosomes come together in homologous pairs, forming tetrads -they overlap in a process called synapsis - crossover of chromatids causing exchange of segments of DNA tetrad
- 50. CELL DIVISION Meiosis I: Chiasma : crossover point
- 51. CELL DIVISION Meiosis I: Metaphase I -chromosomes attach themselves to spindle fibres -chromosomes line up at equatorial plate Anaphase I - Homologous pairs separate and move to opposite poles of the cell Same as mitosis, except the chromosomes are no longer identical . Same as mitosis, except the chromosomes are no longer identical .
- 52. CELL DIVISION Meiosis I: Telophase I -cleavage furrow forms -nuclear membrane reforms -chromosomes do NOT un-condense Same as mitosis
- 53. CELL DIVISION Meiosis II : Second cell division -cytoplasm separates -cells may become gametes Telophase II -sister chromatids from each chromosome separates and moves to opposite poles Anaphase II -chromosomes line up at equatorial plate Metaphase II -more spindle fibres form -chromosomes attach to spindle Prophase II Meiosis Phase
- 54. CELL DIVISION
- 55. CELL DIVISION
- 56. CELL DIVISION
- 57. CELL DIVISION Mitosis vs. Meiosis 46 46 46 46 46 46 23 23 23 23 Diploid (2n) Diploid (2n) Diploid (2n) Diploid (2n) Diploid (2n) Diploid (2n) Haploid (1n) Haploid (1n) Haploid (1n) Haploid (1n)
- 58. CELL DIVISION Division #1 (Meiosis I) Division #2 (Meiosis II) 46 92 92 46 46 23 23 23 23 DNA Replication Synapsis and crossing over Metaphase I, anaphase I, & telophase I Meiosis II Maternal Chromosome A Paternal Chromosome A DNA Replication Sister chromatids Synapsis and crossing over Metaphase I, anaphase I, & telophase I 92 92 46 46 23 23 23 23
- 59. CELL DIVISION Why is meiosis important? allows continuity 2. ensures genetic diversity within population Diversity is generated through… cross-over (makes diverse chromosomes) random assortment (each gamete is different) random fertilization (random sperm meets with random mature egg)
- 60. CELL DIVISION How does this relate to Mendel? Before the process of meiosis was discovered, Mendel’s observations led him to make 2 conclusions: Law of Segregation : 2 alleles for each trait separate during gamete formation (i.e. parents can only pass 1 of their 2 alleles for any trait to their offspring). Monohybrid cross
- 61. CELL DIVISION How does this relate to Mendel? 2)Law of Independent Assortment: Alleles from different chromosomes assort independently during gamete formation. For example, the allele for pea shape and the allele for pea color is passed onto offspring without relation to one-another. Dihybrid cross
- 62. CELL DIVISION How does this relate to Mendel? All daughter cells are different Made possible by the final division in Meiosis II Made possible by different chromosomes having different alleles
- 63. CELL DIVISION How does this relate to Mendel?
- 64. CELL DIVISION New discovery: NASA finds new life form (December 02, 2010) - bacteria GFAJ-1 capable of using arsenic to build its DNA, RNA, proteins, and cell membranes - All other life on Earth is made of six components: Carbon, hydrogen, nitrogen, oxygen, phosphorus and sulfur. - Instead of using phosphorus, GFAJ-1 uses poisonous arsenic for its building blocks - found in Mono Lake, California by NASA scientist Felisa Wolfe-Simon and her team
- 65. CELL DIVISION New discovery: NASA finds new life form (December 02, 2010)
- 66. CELL DIVISION Mistakes during meiosis: Errors during Independent Assortment 46 44 48 22 22 24 24 46 46 46 23 23 23 23 Normal Meiosis Non-disjunction Non-disjunction: Failure of (homologous) chromosomes to separate
- 67. CELL DIVISION Mistakes during meiosis: Errors during Independent Assortment What are the possible zygotes when a normal gamete is joined with a non-disjunct gamete? Non-disjunct egg sperm 22 23 45 Monosomy egg Non-disjunct sperm 23 24 47 Trisomy
- 68. CELL DIVISION Mistakes during meiosis: Errors during Independent Assortment Aneuploidy: A condition that results when there is a missing or extra chromosome, resulting in changes to the normal chromosome number
- 69. CELL DIVISION Mistakes during meiosis: Errors during Independent Assortment Monosomy: A condition in which an individual has only one homologue of a specific pair of homologues
- 70. CELL DIVISION Mistakes during meiosis: Errors during Independent Assortment Trisomy: A condition in which an individual has three homologues of a specific chromosome.
- 71. CELL DIVISION Mistakes during meiosis: Errors during Independent Assortment Polysomy: A condition in which an individual has more than the normal number of a specific chromosome.
- 72. CELL DIVISION Mistakes during meiosis: Errors during Independent Assortment Haploid (n): having one copy of an entire chromosome (e.g. sex cells) Diploid (2n): having two copies of an entire chromosome (e.g. somatic cells) Triploid (3n): having three copies of an entire chromosome Polyploidy: A condition in which an individual has three or more copies of an entire chromosome
- 73. CELL DIVISION Mistakes during meiosis: Errors during Independent Assortment How is it possible to get 3 or more copies?
- 74. CELL DIVISION Broad flat face, slanting eyes, short, growth failure, mental disabilities, congenital heart disease #21 47 Down syndrome Characteristic Affected chromosome Final # of chromosomes Condition
- 75. CELL DIVISION Short, facial hair, undeveloped breast, degenerate ovaries, infertile X chromosome 45 Turner’s syndrome Characteristic Affected chromosome Final # of chromosomes Condition
- 76. CELL DIVISION Tall, longer limbs, poor beard growth, feminized physique, loose chest hairs, underdeveloped penis and testes, infertile X chromosome 47 or more Klinefelter’s syndrome Characteristic Affected chromosome Final # of chromosomes Condition
- 77. CELL DIVISION Normal male, tall, “aggressive” Y chromosome 47 or more Jacob’s syndrome Characteristic Affected chromosome Final # of chromosomes Condition
- 78. CELL DIVISION Normal female, “aggressive” X chromosome 47 or more Super female Characteristic Affected chromosome Final # of chromosomes Condition
Editor's Notes
- #2: Hornets kill bees: http://www.youtube.com/watch?v=L54exo8JTUs&feature=fvwrel Hornets from Hell: http://www.youtube.com/watch?v=R5QxUR-mZVM
- #21: http://www.youtube.com/watch?v=zdDkiRw1PdU&feature=related http://www.youtube.com/watch?v=cDlKrLJjRlY&feature=fvwrel cartoon
- #39: http://www.youtube.com/watch?v=VGV3fv-uZYI
- #65: http://gizmodo.com/5704158/ http://www.nasa.gov/topics/universe/features/astrobiology_toxic_chemical.html?sms_ss=facebook&at_xt=4cf83711808845b3%2C0
- #66: http://gizmodo.com/5704158/ http://www.nasa.gov/topics/universe/features/astrobiology_toxic_chemical.html?sms_ss=facebook&at_xt=4cf83711808845b3%2C0