Looking for a Tutor Near You?

Post Learning Requirement » x
Ask a Question
x

Choose Country Code

x

Direction

x

Ask a Question

x

Hire a Tutor
Kuala Lumpur

PPT On Form 4 Chapter 5 Cell Division

Home > PowerPoint Slides > PPT On Form 4 Chapter 5 Cell Division
Published in: Biology
2,073 Views

In the topic of Cell Division, students will be given a brief introduction to two types of cell division and learn the following: • Identify the phases in a cell cycle • Understanding the processes of mitosis and meiosis • State the importance of mitosis and meiosis • Explain the importance of controlled mitosis • Understanding the process of cloning and its characteristics

Siti F / Penang

5 years of teaching experience

Qualification: Master of Science (MSc) in Molecular Biology, Bachelor of Science (BSc) in Biology, AUSMAT in Biotechnology

Teaches: English, Science, Bahasa Malaysia, Biology, Pendidikan Islam

Contact this Tutor
  1. Cell Division
  2. Mitosis Necessity for production of new cells in living organisms •:• Cells continuously dividing, growing, dying. Dead cells need to be replaced with new cells. Organism grow, change through cell division. •:• Cell division - cells grow, divide, replace dead (existing) cells. Nuclear division - mitosis, mitotic cell division, followed by Cytokinesis - cytoplasmic division. •:• Plants - occurs in meristematic tissues of root tips & bud tips, allow growth, elongation of plant. Animals - occurs in every part of body, Eg; skin produce new skin cells replace dead skin cells.
  3. Significance of Mitosis • Process of nuclear division results in formation of 2 genetically identical daughter cells (all cells have same gene). • Replace dead cells. Eg; skin cells live only 2 weeks. • Repair, replace, regenerate damaged cells. Eg; liver cells regenerate following an injury. • Basis of asexual reproduction. Eg; unicellular organism, Amoeba sp. Produce genetically identical to parent cell — Binary fission. • Increases number of cells, allow growth & development. Eg; multicellular organism, zygote divides & grows eventually complete organism. • 2 daughter cells genetically identical to each other and to that of parent cell. Nucleus contain same number of chromosomes, same gene as parent cell.
  4. Chromosome & Number *Cells divide — Somatic cells & Reproductive cells or gametes. *Somatic cells — all cells except for reproductive cells. *Reproductive cells — formed through Meiosis. *Every cell has chromosome (thread-like structures in Nucleus). *Chromosomal number - number of chromosome (in nucleus) of each species of an individual is constant. *Individuals of same species have same number, but different species have a different number. Eg; onions have 16 chromosomes, fruit fly, 8 chromosomes. *Chromosomal number — diploid, in pair in nucleus, = 2n. Eg; 16. *Gametes — contain half of number, haploid = n. Eg; 8. *Human — Somatic cells have 46 chromosomes, gamete has 23. 2 sets = Parental & Maternal origin = Homologous chromosomes, a member = Homologue, carry genes for trait (Eg; eye color) at same location. 22 pairs = Autosomes, 1 pair = Sex chromosomes *Diploid cells = 2 sets, 46, Haploid cells = 1 set, 23.
  5. Human Male Karyotype Human Female Karyotype li 15 6 13 20 3 4 5 8 9 10 11 12 81 15 16 17 18 19 22 7 13 19 2 8 14 3 9 15 aa 21 4 IC 16 •a 22 5 11 17 6 12 18 14 21 Human cells = • 23 pairs of chromosomes (46 total) • Diploid number of chromosomes • 1 member of a pair donated from Mother, the other one from Father. • 22pairs = AUTOSOMES • I pair = SEX CHROMOSOMES (determines Gender). SEX CHROMOS ES SEX CHROM AUTOSOMES AUTOSOMES smaller Karyotype = a picture of a person's chromosomes (a display of chromosomes). Chromosomes are stained, and examined under the microscope.
  6. Mitosis maintains chromosomal number • Daughter cell has same genetic information (gene, DNA) inherited from parent cell. Gene is carried in chromosome. Contains same chromosomal number & genetic information as parent cell. • DNA — double helix contains genes. • Gene — in chromosome, unit of heritance, must be passed down to its offspring. • Mitosis doubles number of cells without changing genetic content of cell.
  7. Chromosome Gene Nucleus • Chromosome — consists of DNA double helix & protein. • Chromatin — when it is not condensed, visible as thread-like. DNA — carries gene inherit from parents. S phase — DNA replicates, form 2 identical DNA, duplicated chromosome with 2 sister chromatids contains DNA identical copies. Mitosis — 2 sister chromatids separate, become daughter chromosomes. • When cell division begins, chromatin becomes condensed, coiled & folded, compact, thick, easily seen under microscope, attached at centromere.
  8. omo ogouS chromosomes entromere Replication Omo Ous chromosomes Chromosome Genes sister chromatids Sister chromatids of duplicated chromosomes have same alleles for each gene. DNA Sister alleles at a — gene locus Sister DNA replication Homologues have alleles for same genes at specific lcxi.
  9. Cell cycle Cell cycle extends from the time a new cell is produced until time the cell completes a division. 2 major phases: a) Interphase (Gl, S, G2 stage). b) Mitotic cell division or M phase (Mitosis) Interphase •• •• a) b) c) Accounts for 90% of cell cycle. Cells grow larger, prepare for cell division (mitosis). Nucleus is big, well defined. Chromatin — not condensed, visible. Centrosomes form in cytoplasm. Each centrosome consists of a pair of centrioles. Migrate towards opposite poles of cell, formation of spindle fibres. Divided into 3 stages: Gl phase (gap or growth phase 1) S phase (DNA synthesis) G2 phase (gap or growth phase 2)
  10. G, G rmth ONA Synthesis p mp•rations for livi•ion PMS M phase (MITOSIS) CELL DIVISION INTERPHASE Gl staqe Synthesis materials required for cell division — Protein & new organelles. High Metabolic rate. • Cells decide, whether or not to divide, complete cycle to form new cells. If external conditions conducive for growth, then cell enter S phase. • Chromosomes are fine, not visible— Chromatin. S staqe DNA synthesis (gene), Replication. • Duplicated chromosome consists of 2 identical sister chromatids, same DNA. G2 staqe • Cell continues to grow, remain active. • Enzymes, proteins are synthesized. • Cell accumulates energy, complete final preparations for division.
  11. Mitosis M phase can be divided into 2 major a) Mitosis b) Cytokinesis *Has 4 phases : parts: PROPHASE, METAPHASE, ANAPHASE, TELOPHASE
  12. 1) 2) 3) 4) 2n 2n 1) PROPHASE • Chromosomes condense, tightly coiled, shorter, thicker, visible under microscope. •Joined at centromere, 2 sister chromatids. • Spindle fibre forms. • Centrioles (centrosomes) migrate to poles. • Spindle fibre attaches to centromeres. • Nucleolus & nuclear membrane disappears. 3) ANAPHASE • 2 sister chromatids separate at centromere. Pulled apart to opposite poles, shortening of spindle fibres. • When separated = daughter chromosomes, reach poles. • Each pole has a set of a complete & identical chromosomes as parent cell Appears in PAIRS Diploid 2) METAPHASE Chromosomes with 2 sister chromatids, are lined up , arranged randomly at the metaphase (equator) plate. • Spindle fibre fully formed • Each duplicated chromosome (sister chromatids) are attached to spindle fibre. 4) TELOPHASE • Chromosomes start uncoil, become chromatin again. • Spindle fibre disappears. • Nucleolus & nuclear membrane reforms. CYTOKINESIS • Division of cytoplasm form 2 daughter cells, having nucleus by the action of cleavage furrow pinches at the equator of cell.
  13. Cleavage furrow Contractile ring of microfilaments 100 Daughter cells Vesicles forming Wall Of parent cell (a) Cleavage of an animal cell (SEM) cell plate Daughter cells (b) Cell plate formation in a plant cell (TEM)
  14. Importance of controlled Mitosis *Cells must divide in a controlled, orderly manner, distribute exact copy of each of chromosome to new cells. *Because gene carried by chromosomes is necessary for proper functioning of organism. *Mitosis ensure gene content & number chromosomes in parent cells are maintained in daughter cells from one generation to next. *Rate & timing of cell division is important for normal cell growth, development & maintenance. *Different cells divide at different frequencies, Eg; human skin cells divide throughout lifespan while liver cells only divide when necessary to replace damaged or injured tissue. *Each cell has system consist of specific proteins control & phases in cell cycle. *Control system — ensure cell division is complete & cell divides in a controlled manner. Certain genes are involved in protein synthesis, replication in S phase.
  15. Effects of uncontrolled Mitosis *When cells divide repeatedly, without control, regulation, produce cancer cells. *Cancer — • Disease caused by uncontrolled mitosis, due to severe disruption to mechanism controls cell cycle. • Divide freely, uncontrollably. • Compete with surrounding normal cells to obtain sufficient nutrients & energy for their own growth. • Cancel cell that is not destroyed will divide uncontrollably to form Tumour = abnormal mass of cells. • Intrude & spread to other tissues, lead to malfunction of tissues, ultimately death. • Caused by factors: Damage to DNA Gene mutation that control cell division Ionising radiation Eg; X-rays, UV, Gamma ray Chemical compounds — Tar, tobacco smoke Carcinogenic compounds - formaldehyde
  16. Normal cells Controlled growth Single organized layer Cells are differentiated, carry out specialized functions Nuclei & number of chromosomes are normal Cancer cells Uncontrolled growth Multi-layered & disorganized Cells are undifferentiated, not have specialized functions Nuclei & number of chromosomes are abnormal
  17. Application of mitosis *Cloning — process producing clones or genetically identical copies of a cell, tissue or an organism through asexual reproduction not through fusion of gametes. Produce organism with same genetic content & chromosomal number as parent. *Animal cloning — transfer of nucleus from a somatic cell to an ovum or embryonic cell with nucleus removed. sheep named Dolly, one of the successful clones in 1996. Somatic cells Unfertilized egg (mammary gland cells) (ovum) cell is obtained. are removed & grown in low culture medium. Dolly, the cloned sheep of somatic cell donor is born. The nucleus is removed, leave cytoplasm & organelles. Embryo is implanted into a surrogate mother (same breed of sheep as the ovum donor sheep) Electric pulse stimulates fusion between somatic cell + denucleated egg. Cell divides repeatedly forming an embryo
  18. A donor cell is taken from a sheep's udder. Donor Nucleus Egg Cell These tvvo cells are fused using an electric shock. The nucleus of the egg cell is removed. Cloned Lamb An egg cell is taken from an adult female sheep. The ernbryo develops normally it-to a lamb—Oolly Dolly The fused cell begins dividing normally. Embryo The embryo is placed in the uterus of a foster mother. first mammal to have been successfully cloned from an adult cell.
  19. Application of mitosis *Tissue culture technique — plant & animal cells can be extracted & cultured in a nutrient medium outside organisms. Involves cells or tissues growth outside organisms in a suitable culture medium contains nutrients & growth hormones (in vitro — in glasses methods) conducted outside body of organism, in test tube, conical flasks. *Main purpose to produce plant & animal cells through asexual reproduction. Each cell has full genetic potential to form all parts of a mature organism. A single plant develop to become a complete plant. *Different parts of plant can be cultured Eg; shoots, meristemic tissues, leaves, roots, seeds, embryos. Small pieces of plants' leaf, shoot, stem etc. are cut out = Explants. Alternatively, Enzymes used to digest cell walls of tissues (mesophyll) results in naked cells without cell walls = Protoplasts. Explants or protoplast are sterilized, placed in glass container contains * *nutrient, culture medium (glucose, amino acids, minerals etc) for tissue growth, **sterile condition, free from microorganisms that may contaminate tissue culture, *optimum pH & temperature.. Begin to divide by mitosis, produce aggregates of cells into Callus — undifferentiated mass of tissue. Callus Embryo Embryo Plantlet, transfer to soil, grow as adult, Genetic identical
  20. excised piece of isolated cells Ovaview of the Tissue Culture Process
  21. *Thousands of new young plants or cloned plants with desirable characteristics & traits Eg; strong resistance towards diseases can be produced from somatic cells taken from parent plant. All have same gene, characteristics, as parent plant. Large number of identical plants can be produced for commercial purposes. *Genetic engineering, genes of a plant can be altered, engineered to produce higher yields. *Transgenic plants carry a foreign gene has been introduced into their genetic constitution so possess new & different traits. Improved food quality. Eg; soya, wheat, cotton, resistant to herbicides, pests, diseases.
  22. Advantages of Cloning *Multiply copies of useful genes or clones. • E. coli has been genetically manipulated to produce growth hormones. Synthesize large amount of hormone, injected into cows to increase milk quality. *Shorter time in larger numbers of clones. • E. coli is cloned to produce insulin (produced by pancreas, lowers blood glucose concentration, convert glucose to glycogen) especially for diabetes mellitus patients, needs constant supply. • Last time, it was obtained from animals, needs to purify, costly, not enough amount to meet demand. • Gene codes for insulin production inserted into E. coli's genome, multiply rapidly with the desired gene on large scale for commercial purpose. • Each clone contains that gene to synthesize insulin. • Bacteria is lysed, insulin is extracted. • Less expensive, Large quantities, readily available.
  23. *Plants reproduce from seeds take a long time to grow, produce fruits. Cloned plants, can produce flowers & fruits within a shorter period. As clones reach maturity in short period, less time & effort needed to supervise them. *Transgenic crops Eg; wheat, soya bean, cotton are resistant to herbicides, pests & diseases are created. • Plants produce better quality yields, Eg; resistant to larvae, gene codes a protein synthesis that kills larvae that feed on cotton plants. • Delayed ripening in tomatoes, appears fresh & firm, longer shelf life. • Thousands of plantlets with similar resistance to pests & diseases, planting Genetically modified (GM) crops. + Involve vegetative reproduction does not need pollinating agents. Propagation takes place any time. *Control or overcome environmental pollution, cutting down the cost & time for cleaning. Eg; gene for lipase synthesis isolated from animals, inserted into bacterial genome, create bacteria that can clean up oil spills in ocean, break down toxic waste materials, help clean up toxic waste dumps. Eg; bacteria removes sulphur from coal.
  24. Disadvantages of Cloning •Ethical & moral issues regarding cloning. Religious groups & organizations questioned, strongly opposed it. *Long-term side effects of using genetically modified viruses & bacterial clones in medicines, industries not yet known. *Long-term effects & safety aspects of releasing bacterial clones to environment to solve problems related to environment such as pollution, not yet known, organisms may mutate, become dangerous to environment & organisms. *Clones do not show any genetic variations. Eg; plant clones have adapted to current environment. If a drastic change in future, clones may be wiped out entirely, unable to adapt anymore to the changes. *Clones have same level of resistance towards certain diseases. If new disease or pest emerge, all clones may be eliminated, not resistant to new ones. *New clones undergo natural mutations can endanger mankind & environment, may disrupt natural equilibrium of ecosystem. *Contain genes resistant to herbicides. Genes may be transferred to weeds through viruses, weeds could be resistant to herbicides too. *Cloned animals have a shorter lifespan. Research still find solution to prolong it.
  25. Meiosis Significance of Meiosis *Offspring to possess same chromosomal number as their parents, reproductive organs that produce gametes must undergo meiosis — half, haploid number. *Meiosis — process of nuclear division reduces number of chromosomes in daughter cells to half that of parent cell. Produces Gametes=Haploid cells = n. From 2n to n. Because contain half of genetic material (gene), number of chromosomes of the Parent cells = Diploid cells = 2n. *Gamete receives 1 chromosome from a pair of homologous chromosomes. Contains 23 chromosomes = Haploid number of chromosomes = n. *During sexual reproduction, Fertilization = fusion of 2 gametes (Sperm + Ovum) restores complete number of chromosomes & genetic material (gene) forming diploid zygote = 46 chromosomes. Offspring inherits traits from both parents to ensure a continuation of life.
  26. Process of Meiosis + Meiosis contains 2 separate nuclear divisions: a) Meiosis I — Prophase l, Metaphase l, Anaphase l, Telophase l. b) Meiosis Il — Prophase Il, Metaphase Il, Anaphase Il, Telophase ll. Begins with a single diploid parent cell. Produce 4 Haploid cells, each has different genes, different from the others, and from the parent cell. Undergoes Interphase too and DNA replicates once.
  27. Meiosis Meiosis I 2 stages 2n = DIPLOID = 46 chromosomes DNA replication INTERPHASE Meiosis Il CYTOKINESIS MEOISIS 1 SAME LIKE MITOSIS CYTOKINESIS MEOISIS 11 n = HAPLOID = 23 chromosomes GAMETES
  28. 1) 2) 3) 4) 2n Prophase I Metaphase I Anaphase I Telophase I Cytokinesis 1) PROPHASE I • Chromosomes condense, tightly coiled, shorter, thicker, visible under microscope. • Homologous chromosomes come together form bivalents through process —Synapsis. One paternal, the other one, maternal. • Bivalent consists of Tetrad consists of 2 Homologous chromosomes (Pair of 2 sister chromatids). • Crossing over — DNA or gene exchange between Non-sister chromatids, occur at any locations on chromosome, results in new gene combinations on chromosome. • Chiasmata — points where cross over occurs. • Nucleolus & nuclear membrane disappears. • Centrioles migrate to poles. 4) TELOPHASE I 2) METAPHASE I • Homologous chromosomes pair align randomly at metaphase plate, lined up side by side as tetrads. Attached to spindle fibres. Centromeres do not divide. 3) ANAPHASE I • Spindles are shortened, pull. • Homologous chromosomes separate. Homologous chromosomes, each containing 2 sister chromatids, move to separate poles. • Centromeres do not split and sister chromatids remain paired. • Sister chromatids become daughter chromosomes. • Each pole receives the HALF number of chromosomes as the parent cell. Meiosis Il The chromosomes are at the poles. • Each pole has haploid daughter chromosomes. • Spindle fibre disappears. • Nucleolus & nuclear membrane reforms.
  29. CYTOKINESIS • Resulting in 2 haploid daughter cells. Each cell has 1 chromosome from a homologous pair. • No Interphase before Meiosis Il starts. No DNA replication. Chromosomes remained condensed. Meiosis Il *Each of the 2 daughter cells is now haploid (n), with HALF the number of chromosomes per nucleus. some species, the nuclear membrane briefly forms around the chromosomes. + The cell now proceeds into meiosis Il, with the chromosomes remaining condensed. + Meiosis I proceeds directly to meiosis Il without going through interphase.
  30. 1) 2) 3) 4) Prophase Il (#2) Metaphase Il Anaphase Il Telophase Il CytokinesiS Meiosis Il, resembles Mitosis Chromosomal numbers, which have already been reduced to Haploid (n) by the end of meiosis l, remain unchanged after this division. 1) PROPHASE Il • Nucleolus & nuclear membrane disappears. • Spindle fibre reforms 3) ANAPHASE Il 2) METAPHASE Il Chromosomes as sister chromatids are aligned randomly at metaphase plate. Still attached to spindle fibre at centromere. • Spindles are shortened. • Chromatids of each chromosome have separated (divide at the centromeres). • The resulting chromosomes, each with one chromatid moving towards the poles. • Each pole receives the same number of chromosomes as the parent cell. CYTOKINESIS 4) TELOPHASE Il • Nucleolus & nuclear membrane are reforming. • Spindle fibre disappears. • 4 haploid daughter cells are formed. Each contains half number chromosomes, gene from parent cell. These cells Gametes.
  31. Single chromatid Daughter cells GAMETES These 4 cells: • HAPLOID CELLS (Daughter cells) = HALF no. of chromosomes of the Parent cell (23 chromosomes). • Cells are not identical, crossing over in prophase I and random arrangements of bivalents in metaphase I leads to different genetic composition of these cells. • In humans, meiosis produces genetically different haploid daughter cells, each with 23 chromosomes that consist of one chromatid. These haploid cells become unfertilized eggs in females and sperm in males. The genetic differences ensure siblings of the same parents are never entirely genetically identical.
  32. Blue = AA Blue = Aa Red = aa Synapsis Recombination can occur between these two strands of chromosomes Red = Aa Chiasma Chiasma Synapsis = process when homologous chromosomes pair up. • Crossing over = process in which non-sister chromatids exchange segments of DNA. This leads to genetic recombination (exchange of genetic material) between the chromatids (1 from Father, 1 from Mother). BLUE and RED chromosomes, which originally carried AA and aa alleles, respectively, now carry Aa alleles in both chromosomes at the end of prophase l. • Note that these bivalents have 2 chromosomes and 4 sister chromatids, with 1 chromosome originating from each parent. • The point where a crossover occurs is called a chiasma (plural chiasmata).
  33. Spermatogenesis diploid cell dou e chromatids 46 chromosomas Primary spermatocyte 46 c h romosomas Oogon ia cell Prima OOCVte (released haploid cells 22+ x Oogenesis In embtyo Present at birth MEIOSIS I cornpletion) First polar MEIOSIS Il (stimulated by sperm cells) MEIOSIS Seco double chromatids 23 c h romosomes MEIOSIS 11 haploid cells Single chromatids 23 22+Y Sperm develop in in coiled tubes called seminiferous tubules FERTILIZATION 22+ x 22+X 22+ x During oogene-5i5, an ovum develops in the ovary. The secondary is the Stage released by the ovary during ovulation. Ovu m Female Sperm
  34. Sex chromosomes pair at meiosis I X chromosome Meiosis I Meiosis Il 50% of sperm contain X chromosome Y chromosome 50% of sperm contain Y chromosome
  35. Sex Chromosomes The male gametes or sperm cells in humans and other mammals contain one of two types of sex chromosomes. They are either X or Y. • The female gametes or eggs however, contain only the X sex chromosome. The sperm cell determines the sex of an individual in this case. If a sperm cell containing an X chromosome fertilizes an egg, the resulting zygote will be XX or female. If the sperm cell contains a Y chromosome, then the resulting zygote will be XY or male.
  36. MITOSIS Somatic cells Produce new cells for growth & repair Chromosomes arrange individually at plate Sister chromatids separate No No SIMILARITY DNA replicates only once DIFFERENCES MEIOSIS Cell type Role Metaphase of Mitosis Metaphase I Anaphase of Mitosis Anaphase I Synapsis Crossing over Cells in reproductive organs Produce gametes for sexual reproduction Homologous chromosomes arrange side by side at plate Homologous chromosomes separate, sister chromatids still remain attached Yes, to form bivalents Yes, between non-sister chromatids
  37. 1 2 46, diploid (2n) Identical No DIFFERENCES No. of divisions 2 No. of daughter cells 4 Chromosome number of daughter cells Genetic content Genetic variation 23, haploid (n) Different
  38. Importance of Meiosis Ensure diploid number chromosomes is maintained from one generation to next. Provide genetic variations. Leads to genetic recombinations: a) Prophase I — Crossing over. Genetic material exchange between non-sister chromatids of a bivalent. Formation of new gene combination on a chromosome. b) Metaphase I — Random arrangement or Independent assortment. Homologous chromosomes arranged independently, randomly at metaphase plate. Gametes have different gene combinations. Random fertilization of ovum by a sperm results in genetic variation in organisms.
  39. Appreciating movement of chromosomes Asexual reproduction through Mitosis produce offspring identical to parent. Sexual reproduction through Meiosis produce genetic variability in offspring. If meiosis does not occur properly, gametes formed will have abnormal number of chromosomes. Zygote formed later be abnormal. Eg; Down's syndrome — result of extra chromosome 21 , each body cell has a total of 47 chromosomes instead of 46. Have certain characteristics include small body & mental retardation. Certain environmental agents — radiation, chemicals, food contains preservations, carcinogenic disrupt process mitosis & meiosis, change DNA structure. Down Syndrome Karyotype 9 10 11 15 16 17 18 19 21 22 trisomy

Need a Tutor or Coaching Class?

Post an enquiry and get instant responses from qualified and experienced tutors.

Post Requirement

Related PPTs

Upload PPTs

If you have your own PowerPoint Presentations which you think can benefit others, please upload on MyPrivateTutor. For each approved PPT you will get 50 Credit Points and 50 Activity Score which will increase your profile visibility.

Upload Now