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CELL DIVISION AND REPRODUCTION Unit 7 FLASHCARD WARMUP Chromosome DNA is coiled to conserve space and this structure is called a chromosome. When the DNA copies to prepare for mitosis, the two copies are each called chromatids and are connected for a while in a doubled chromosome. REASONS FOR CELL DIVISION 1. Maintain a workable volume to surface area ratio; volume increases faster than surface area in cells a larger surface area: volume ratio is preferable. 2. Growth- multicellular organisms must increase in the number of cells to grow 3. Repair and replacement of cells lost due to injury or cell death requires cell division. Larger surface area: volume ratio Smaller surface area: volume ratio EUKARYOTIC CELL CYCLE Interphase: Longest part of the cell cycle; DNA replication takes place, carries out life functions Chromatin: condensed DNA and proteins, (will form a chromosome) Chromatid: identical copies of DNA making up a duplicated chromosome, attached at centromere Doubled chromosome: nicely packaged and duplicated DNA MITOSIS Prophase: Chromosomes visible, spindles form Metaphase: chromosomes move to middle (equator) of the cell Anaphase: doubled chromosomes separate, chromatids move to opposite ends of cell Telophase:spindles breakdown, nuclear envelope appears Cytokinesis: Division of cytoplasm Plant Cells: cell plate is produced and will become cell wall Results: Two identical cells ,diploid (2n) –ex. Our cells have 46 chromosomes PROBLEMS WITH MITOSIS Cancer: Uncontrolled cell division A cancerous lung tumor Benign when it is localized to one area, malignant when cancer cells are in blood stream and move to another part of the body TICKET OUT THE DOOR Identify the stages of the cell cycle in the picture. Write out the correct order as given and match the letter with the correct phase. Interphase prophase metaphase anaphase telophase FLASHCARD WARMUP Mitosis Meiosis This type of ASEXUAL cell division makes exact copies of a cell. It is part of a cell’s life cycle, after normal growth. The phases of mitosis are Prophase, Metaphase, Anaphase, and Telophase. (PMAT) One parent cell divides to become two daughter cells. A form of sexual reproduction. This type of cell division creates gametes or sex cells. These are haploid or have ½ the number of chromosomes so that the zygote has the correct number after fertilization. TYPES OF REPRODUCTION Asexual: one source of genetic material, identical daughter cells Advantages: reproduction is fast, less energy needed, no mate needed, Disadvantages: lack of genetic variation (one thing could wipe out entire population) TYPES OF ASEXUAL REPRODUCTION Binary Fission: cell divides into 2 equally sized cells Budding: produce smaller cells than parents (ex. hydra and yeast) Sporulation - produces spores TYPES OF ASEXUAL REPRODUCTION Vegetative propagation: a portion of one plant produces a new identical plant Regeneration: part of animal is repaired through cell division SEXUAL REPRODUCTION Sexual: two sources of genetic material, makes four haploid sex cells (gametes) Gametes: sperm and egg Advantages: genetic variation, Disadvantages: requires more time for mating, risk of unfavorable genetic combinations Fertilization TICKET OUT THE DOOR Give two examples of asexual reproduction and briefly explain. What are the advantages and disadvantages of asexual reproduction? FLASHCARD WARMUP Homologous Chromosomes Diploid and haploid Each species has a specific number of chromosomes. Humans have 46 chromosomes in 23 homologous pairs. Each homologous pair has one from the mother and one from the father. Homologous chromosomes have the same traits. Somatic (body) cells are diploid, meaning that they have pairs of chromosomes. When a cell undergoes meiosis to prepare for sexual reproduction, the chromosome number must be reduced by half, creating a haploid cell. MEIOSIS: REQUIRES 2 DIVISIONS: PHASES THE SAME AS MITOSIS Meiosis I (1st division): Reduces the chromosome number; Result: 2 genetically different daughter cells (1n) 23 chromsomes (doubled genetic material) Meiosis Animation Meiosis II (2 division): Reduces the genetic material Result: _all genetically different MEIOSIS ALLOWS FOR LOTS OF VARIATION (DIFFERENCES) Variation as a result of: Crossing Over: a part of one chromosome can switch places with the same part another homologous chromosome . Random Assortment: of chromosomes allows a mix of chromosomes from both parents Random Fertilization : of any egg by any sperm allows for lots of variation PROBLEMS WITH MEIOSIS: Mutations: changes in the DNA before meiosis or mitosis begins Nondisjunction: homologous chromosomes do not separate resulting in one too many or one too few chromosomes Ex. Down syndrome : trisomy 21 Karyotype- a picture of the chromosomes NONDISJUNCTION COMPARISON OF MITOSIS AND MEIOSIS TICKET OUT THE DOOR How many cells are produced as a result of Meiosis? If a parent cell has 4 chromosomes and goes through MEIOSIS, how many chromosomes would the daughter cells contain? Meiosis is uses for (sexual or asexual) reproduction?