BIO 1 - Cell Cycle, Mitosis and Meiosis.pdf

GENERAL BIOLOGY 1 ERNEST G. FORTU, LPT  CELL CYCLE MITOSIS  Learning Objectives 1. identify the phases 2. characterize the 3. identify the control of the cell cycle; phases of the cell cycle; points in the cell cycle; 4. determine the most 5. create a cell cy...

GENERAL BIOLOGY 1 ERNEST G. FORTU, LPT  CELL CYCLE MITOSIS  Learning Objectives 1. identify the phases 2. characterize the 3. identify the control of the cell cycle; phases of the cell cycle; points in the cell cycle; 4. determine the most 5. create a cell cycle 6. realize the significant event wheel as a tool in importance of cell cycle happening in a given learning the cell cycle and their control points. control point; and its control points; Cell cycle has two main phases, Mitotic Phase and Interphase During interphase, the cell grows, organelles are being copied, and the genetic material (DNA) is replicated.  During the mitotic phase, the replicated DNA, the cytoplasm, and the organelles in it are separated. Then finally, the cell divides. The new identical daughter cells are formed. INTERPHASE  The G1 Phase (Gap 1) or First Gap. It is in G1 that the cell grows, and the organelles are duplicated. It is also in G1 that the cell carries out normal metabolism, produce RNA, and synthesize proteins.  The G1 Phase (Gap 1) or First Gap. The “decision making step” when the cell decides if it will start a nex cycle, rest or permanently exit the cell cycle to become differentiated cell (G0)  The S Phase (Synthesis) During the S phase, the genetic material DNA is replicated or copied. At this stage also, the centrosome is duplicated.  The G2 Phase (Gap 2) or Second Gap During this phase, the cell continues to grow and prepares for mitosis to happen  MITOTIC PHASE Phase where the cell divides via cytokinesis to produce two daughter cell.  MUTATION Mutations happen when there are mistakes in the duplication or distribution of the chromosomes or genes. The mutation in the abnormal cell could be passed on to every new cell produced. The cell has internal control mechanism at three cell cycle control points so that the abnormal cell could not continue to divide and harm other cells,  CELL CYCLE CONTROL POINTS A control point, or checkpoint, in the eukaryotic cell can stop the cell from moving to the next stage until conditions are favorable. The control points check if the cell grows with the right cell size, the chromosomes are replicated and are exact, and they are accurately separated at mitosis.  Regulator Molecules of the Cell Cycle The regulator molecules can cause the cell cycle events to stop or to continue. Some of these important molecules are cyclin, CDK, and Rb. Cyclins and cyclin dependent kinases (CDKs) are proteins that promote events in the cell cycle. They carry on positive regulation in the cell cycle. Rb (or retinoblastoma protein) is one of the proteins that is considered a negative regulator. Negative regulators stop the cell cycle from moving forward. Negative regulator molecules, like Rb, function mainly at the G1 control point where the cell is prevented from entering the S phase. This is until damaged DNA is repaired. What happens when the control points of the cell cycle do not work?  The Cell Cycle and Cancer Cancer is a disease that results when cell division becomes uncontrolled. Mutated cells go unchecked in control points and divide out of control. They usually clumped or grouped together to form tumors that can affect and destroy normal cells.  You probably had experienced your knee scraped because of an accident. How long did your abrasion (gasgas or galos in Tagalog) heal? An abrasion is a kind of wound (sugat). WHAT DO YOU THINK IS THE REASON WHY OUR WOUND HEALED? Mitosis  Eukaryotic Chromosomes Every organism possesses a definite number of chromosomes. For example, each cell in in the body of a human being contains 46 chromosomes (except the human sperm cell and egg cell. The DNA (Deoxyribonucleic Acid) in the chromosomes of eukaryotes is associated with various proteins, including histones that is involved in organizing chromosomes.  Chromatin When a cell is not undergoing division, the DNA within the nucleus is in its loosed form and forms a tangled mass of thin threads called chromatin. Before mitosis begins, chromatin becomes chromosomes that are highly coiled and condensed.  What is mitosis? Mitosis is a type of cell division that happens in somatic or body cells. In both plants and animals, mitosis is required during the development of a single cell into an individual. The main purpose of mitosis is to produce more cells for growth, repair, and for development.  Interphase Nucleus A cell spends the most time in this phase. The DNA in Chromosome the chromosomes copies itself ready for cell division. The chromosomes then become thicker and start to coil.  Prophase Aster The chromatin fibers have condensed into Centrioles discrete chromosomes. The chromosomes appear as two identical sister chromatids Nuclear united along the centromeres. membrane Centrioles  The nucleolus disappears and the nuclear envelope starts to disintegrate.  The spindle begins to form at the opposite poles and the two centrioles migrate away from one another.  Metaphase The nuclear membrane disappears completely.  The centrioles have finally reached their Centromere respective opposite poles.  The polar spindle fibers continue to extend Spindle fiber from the poles to the center of the cell.  The chromosomes begin to move randomly until they finally attach to the polar spindle fibers from both sides of their centromeres. Chromosome  The chromosomes align at the imaginary plane that is perpendicular and found midway between the spindle’s two poles called metaphase plate or equatorial plate.  Cell membrane Anaphase The two sister chromatids start to move away from each Chromatid other at the centromere, giving rise to two daughter “full” chromosomes.  The daughter chromosomes begin to move toward the spindle poles located at the opposite ends of the cell.  At the end of anaphase, each pole contains an equal and complete set of chromosomes. Telophase The spindle fibers disappear and the diploid daughter nuclei start to form at the two poles of Cell membrane the cell.  The nuclear envelope starts to appear around the daughter chromosomes. The chromosomes uncoil to become chromatin.  The nucleolus appears in each daughter cells.  Karyokinesis or the division of one nucleus to genetically identical nuclei is completed. It is Nuclear membrane followed by the process cytokinesis.  Cytokinesis Cytokinesis is the division of the cytoplasm. After mitosis, the two daughter cells received a share of the cytoplasmic organelles that duplicated during interphase. The phases of mitosis MEIOSIS  What is meiosis? Meiosis is a cell division that occurs in a sexually mature organism. In this process, the haploid number of chromosomes reduces to become haploid gametes. Why is it important? Meiosis makes sure that all organisms produced via sexual reproduction contain the correct number of chromosomes - half from each parent. PROPHASE 1 The chromosomes condense and the nucleolus breaks down. The centriole forms spindle fibers. Homologous chromosomes undergo pairing or the process of synapsis. The homologous chromosomes have the same length and position of the centromere. These homologous chromosomes came from the father and the mother. One paired homologous chromosome is composed on four sister chromatids, which is called a tetrad. PROPHASE 1 Crossing over between the two non-sister chromatids takes place. Crossing over is the swapping of genetic material between non- sister chromatids along the point called chiasmata. METAPHASE 1 The paired homologous chromosomes have moved toward the metaphase plate or at the center of the cell. Kinetochores, protein complexes outside the centromeres are present and attached to the spindle fibers.  ANAPHASE 1 Chromosome pairs separate and move to opposite ends of the cell. Since there are 46 chromosomes in human, 23 will move to the different poles. This means that only half of the number of chromosomes will remain in each cell.  TELOPHASE 1 Two new nuclei form around each set of chromosomes. Finally, the two daughter cells completely divide. There is an equal number of chromosomes found in each daughter cells. The cytoplasm splits and two (haploid) daughter cells are formed. INTERKINESIS Interkinesis is a process similar to interphase between mitotic divisions except the replication of DNA since chromosomes are already duplicated. This is considered as a short pause between the two phases of meiosis.  PROPHASE 2 Phase 2 happens to allow 4 haploid sex cells (sperm and egg cells) to be created. The chromosomes condense and the nucleolus breaks in both cells. The chromatids begin thickening and shortening. The centrioles move to the opposite poles and the spindle fibers arrange to prepare for the next phase  METAPHASE 2 This occurs to ensure sister chromatids separate in the next stage. The two kinetochores of each centromere bind to the spindle fibers from the opposite poles. The chromosomes move until they are on the metaphase plate.  ANAPHASE 2 Sister chromatids separate and move to opposite ends of the cell. The centromeres separate, allowing the microtubules attached to the kinetochores to pull and move to the poles. The sister chromatids become sister chromosomes after moving towards the end of the opposite poles.  TELOPHASE 2 Four new nuclei form around each set of chromosomes. The spindle fibers disappear. The nuclear envelope starts to form around the daughter chromosomes.. The cytoplasm split and four (haploid) daughter unidentical cells are formed.  THE WHOLE PROCESS PROPHASE ANAPHASE ANAPHASE PROPHASE METAPHASE TELOPHASE TELOPHASE METAPHASE FIRST PHASE SECOND PHASE APPLICATION OF MITOSIS AND MEIOSIS  GROWTH AND DEVELOPMENT The number of cells increases by the process of mitosis, enables the growth of a single organism to become a complex multicellular organism. After the union of egg cell and sperm cell, an embryo will be formed. This embryo will continuously grow to become an organism using mitosis.  CELL REPLACEMENT Cells are constantly lost and needs to be replaced by new cells in the body. Example, red blood cells need to be replaced since they die after 120 days of living in the body and the skin cell was replaced after 27 days.  CELL REGENERATION Some organisms use mitosis to replace the damaged part of the plant or animal tissues. Example, starfish was able to regenerate a whole new limb through the process of mitosis.  ASEXUL REPRODUCTION There are organisms such as hydra which uses mitosis to produce its own genetically identical offspring. In hydras, a bud is developed from the parent’s body. It remained attached until it becomes fully grown. When it gets matured, the bud will be separated from the parent’s body. The newly developed organism is genetically identical to the parent. APPLICATION OF MITOSIS CLONING Cloning is a process of getting genetic material or information from one living organism for the purpose of creating an identical copy of it. Gene cloning also known as DNA cloning, is the process of producing copies of genes or segments of DNA. A gene from one organism is inserted to a carrier called as vector. Reproductive cloning is a process of producing a copy of the whole organism. Therapeutic cloning is a process of producing embryonic stem cell for creating or replacing tissues.  ENTER VIRTUAL LABORATORY APPLICATION OF MITOSIS TISSUE CULTURE Tissue culture is a method of transferring tissue fragments of animals or plants to an artificial environment to continue its survival and functions Cells are cultured in controlled conditions that provide a conducive environment for growth and multiplication. The controlled conditions often include proper supply of nutrients, pH medium, adequate temperature, and proper gaseous and liquid environment. APPLICATION OF MITOSIS TISSUE CULTURE Majority of the plant tissue culture are used to propagate plants, eliminate diseases, and improve the propagation of plants. Plant tissue culture is considered to be most efficient technology for agriculture and industry. APPLICATION OF MITOSIS STEM CELL REGENERATION Stem cells are cells that have the ability to renew themselves through the process of mitosis and can differentiate into different range of specialized cell types. There are two classifications of stem cells depending on their ability for differentiation: totipotent, pluripotent, multipotent, and unipotent. TOTIPOTENT AND PLURIPOTENT STEM CELLS Totipotent, also known as omnipotent cells, are cells that can differentiate into embryonic tissues and can generate a complete organism. An example of totipotent cell is a fertilized egg cell. Pluripotent stem cells are cells that can self-renew and can generate into the three germ layers: ectoderm, endoderm, and mesoderm, from which all tissues and organs develop. Multipotent stem cells are cells that can also self- renew but can differentiate only to related family of cells. Example is the mesenchymal stem cells that can give rise to bones, cartilage, and circulatory system. If cells can differentiate into only one type of cell, the cells are classified as unipotent stem cells. SIGNIFICANCE OF MEIOSIS FORMATION OF GAMETES WITH DIPLOID CHROMOSOMES Meiosis allows a diploid cell to reduce into haploid gamete, which when combined with another haploid gamete after fertilization, will create a diploid zygote. SIGNIFICANCE OF MEIOSIS ENABLES GENETIC DIVERSITY The crossing over during Meiosis allows the mixing of genetic material from both paternal and maternal genes, having the offspring receive daughter chromosomes with recombined genes and have the different sequence of alleles. Recombination helps keep the health of the population: resistance to diseases, pests, and other stresses. Maintaining diversity gives the population a protection against change, providing each individual the flexibility to adapt. SIGNIFICANCE OF MEIOSIS ENABLES GENETIC DIVERSITY SIGNIFICANCE OF MEIOSIS ENABLES GENETIC DIVERSITY SIGNIFICANCE OF MEIOSIS REPAIR OF GENETIC DEFECTS The recombination that occurs in meiosis helps in the repair of genetic defects in the next generation. If a genetic defect is present from either one of the parent’s allele, recombination can replace this allele with the healthy allele of the other parent, allowing to produce a healthy offspring. DISORDER AND DEFECTS OF MITOSIS AND MEIOSIS CANCER Cancer is a cellular growth disorder that resulted from the uncontrolled cell division. Its development and progression are linked to a series of changes in the activity of cell cycle regulators. Compared with normal cells, cancer cells can multiply even without growth factors and growth-stimulating protein signals in a culture. It can make their own growth factors to sustain themselves. Cancer cells can also undergo the process of metastasis, which refers to the ability of cells to migrate to other parts of the body. CANCER Cancer cells fail to undergo the process of apoptosis or programmed cell death. Cells become cancerous after succeeding mutations accumulated in the various genes. Due to mutation, cancer cells can make more copies of itself. CHANGE IN CHROMOSOMES NUMBER Another factor that increases the amount of variation among offspring is mutation. Chromosomal mutations include changes in the number of chromosomes and changes in the chromosome structures. When an organism contains correct number of chromosomes, it is known as euploidy. Changes in the number of chromosomes include polyploidy and aneuploidy. A. POLYPLOID Polyploid organisms are named according to the number of sets of chromosomes they have. These are triploid (3n) when it has three sets of chromosomes; tetraploid (4n) when it has four sets of chromosomes; and pentaploid (5n) when it has five sets of chromosomes, Polyploidy is common among plants such as corn, watermelon, strawberry, and bananas. A. ANEUPLOIDY When an organism has more or less than the normal numbers of chromosomes, it is called as aneuploid. There are two states of aneuploidy: monosomy and trisomy. Monosomy (2n – 1) occurs when an individual has only one of a particular of chromosome, and trisomy (2n + 1) occurs when an individual has three of a particular chromosome. A. ANEUPLOIDY Monosomy and trisomy are caused by nondisjunction during Meiosis I, when both members of the homologous pair go into the same daughter cell, or when during Meiosis II when the sister chromatids fail to separate and both chromosomes go into the same gamete.  MONOSOMY An abnormality in the chromosomes where there is a single chromosome in place of a homologous pair. In humans, a monosomy occurs when a gamete containing 22 chromosomes (n-1), instead of 23 chromosomes, fertilizes with a normal gamete (n).  TRISOMY An abnormality in the chromosomes which there are three homologous chromosomes in place of a homologous pair. A trisomy happens when a gamete containing 24 chromosomes (n+1), instead of 23 chromosomes, fertilizes with a normal gamete (n).  TRISOMY 21 DOWN SYNDROME  TRISOMY 13 PATAU SYNDROME  TRISOMY 18 EDWARD SYNDROME  CHANGES IN SEX CHROMOSOME NUMBER Turner syndrome (XO) is a chromosomal condition that affects females. It results when one normal X is present in the cell of the female and the other sex chromosome is missing or structurally altered. Usually, it affects the development of the individual before and after birth.  CHANGES IN SEX CHROMOSOME NUMBER Klinefelter syndrome is a condition that affects mostly boys. It resulted from the presence of an extra X- chromosome in cells. Individuals with Klinefelter syndrome have the usual X and Y chromosomes, with additional one X chromosome, for a total of 47 chromosomes (XXY). CHANGES IN SEX CHROMOSOME NUMBER Poly-X females, also known as superfemale, is a condition where an individual has more than two X chromosomes. Females with this condition may have XXX or XXXX sex chromosomes  CHANGES IN SEX CHROMOSOME NUMBER Jacobs syndrome is a condition where males have XYY sex chromosomes. This disorder happens because of the nondisjunction during spermatogenesis. These individuals are sometimes called supermales. CHANGES IN SEX CHROMOSOME NUMBER THANK YOU!