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Q: What is the difference between a diploid and a haploid cell? A haploid cell has half the number of chromosomes in a diploid cell. Today: Beginning Unit on Cell Reproduction Power Point Notes: Chromosomes Homework: 8.2 Section Review 1-6, 8 Fluorescent In-Situ Hybridization (FISH) identification of human chromosomes Cell Reproduction: Chromosomes Chromosome - replicated DNA that is condensed, coiled and wrapped around histone proteins - replicates and condenses when the cell is about to divide Histones - Proteins that help maintain the shape of the chromosome. - Aid in tight packing of DNA. Chromosome Structure Chromatid - each half of the chromosome Centromere – point where chromatids attach Chromatin – Thin, uncoiled strands of DNA and protein – This form of DNA is found during interphase of the cell cycle Chromosome Numbers Autosomes - all non-sex chromosomes. - Humans have 22 pairs of autosomes Sex Chromosomes - Genetic information that determines gender of an organism - In humans, Females have XX chromosome pair; males have an XY pair - 1 pair of sex chromosomes - Humans have a total of 23 pairs of chromosomes. 2n Chromosomes Honeybee (female) – 32 Adder’s Tongue Fern - 1262 Common Frog - 26 Human - 46 Cat - 38 Maize - 20 Does more chromosomes does bigger Chromosome number mean anot or more complicated organism? determine complexity of organism Animal Chromosome number (2n) 1. Ascaris megalocephala (horse roundworm) 2 2. Drosohila melanogaster (fruit fly) 8 3. Musca domestica (house fly) 12 4. Rana hexadactyla (frog) 26 5. Apis mellifera (honey bee — female) 32 6. Hydra vulgaris 32 7. Fells domestica (cat) 38 8. Pattus rattus (rat) 42 9. Homo sapiens (man) 46 10. Bos indicus (cow) 60 11. Canis familiaris (dog) 78 12. Columbia livia (pigeon) 80 13. Amoeba proteus 250 14. Aleucantha (radiolarian) 1600 Plant Chromosome number (2n) 1. Mucorheimalis (bread mold fungus) 2 2. Penicillium notatum (fungus) 4 3. Pisum sativum (pea) 14 4. Zea mays (maize) 20 5. Oryza sativa (rice) 24 6. Lycopersicon (Tomato) 24 7. Solanum tuberosum (potato) 48 8. Saccharum offtinalis (sugarcane) 80 9. Ophioglossum (Adder’s tongue fern) 1262 Chromosome Numbers cont. • HOMOLOGOUS CHROMOSOMES – Two chromosomes that are the same size, shape and DNA makeup • DIPLOID – contain both chromosomes of a homologous pair. “2N” • HAPLOID – contain only one of the chromosomes of a homologous pair. “1N” Karyotype A photomicrograph of the chromosomes in a normal dividing cell found in a human. Does this karyotype appear to be male or female? karyotyping Trisomy 21, a chromosomal abnormality indicative of down syndrome Karyotyping Questions: • What characteristics did you use to pair up the Chromosomes? • How many autosomes are there? How many sex chromosomes? • Is the organism male or female? What sex chromosomes do females have? Males? • Why are Karyotypes impt for geneticists? • What disease would be caused if you had three chromosomes on 21? Q: What is the difference chromatids, centromeres, and chromatin? Chromatids are the halves of the chromosomes, centromeres are where the chromatids are joined, chromatin is the coiled up DNA that makes up the chromatids/chromosomes Today Power Point Notes: Cell Division Prokaryotes vs. Eukaryotes Homework: draw binary fission p 154, and cell cycle with bulleted notes p 155. Cell Division In Prokaryotes - Prokaryotes use binary fission, the division of a prokaryotic cell into two offspring cells - Cell membrane divides - Prokaryotes do no have a nucleus Cell Division in Eukaryotes Mitosis – results in new cells with genetic material identical to the original cell Asexual reproduction – the production of offspring from one parent Meiosis – occurs during the formation of gametes Gametes – haploid reproductive cells Q: What are the stages of the cell cycle (included in interphase and cell division) in order? G1, S, G2, Mitosis, and Cytokinsis. Also G0 Today: Cell Cycle, Mitosis Homework: Draw and label stages of Mitosis and Cytokinesis, with 3-4 notes for each. Print: Graphic organizer for Thurs, Meiosis flipbook for Fri. Cell Cycle Interphase - the time between divisions - the cell spends most of its time in interphase Cell Division - mitosis and cytokinesis How long does mitosis take? It depends on cell type and culture conditions. Cell Cycle Interphase • G1 stage of interphase – Cell grows to normal size – Cell carries out regular functions (protein synthesis, etc…) • S stage – DNA is synthesized • G2 stage – Organelles are replicated, preparing for cell division • G0 stage – Cells stop dividing, sometimes permanently (ex: nerve cells) G1 → S → G2 OR G 1→ G 0 Mitosis Division of the cell nucleus in which chromosomes of the parent cell divide into two identical daughter cells http://www.johnkyrk.com/mitosis.html http://www.cellsalive.com/mitosis.htm Prophase 1. Nucleolus and nuclear membrane disappear 2. Chromatin condenses to form chromosomes 3. Centrioles and spindle fibers appear - Centrioles are not in plants. Metaphase 1. Kinetochore fibers move the chromosomes to the center of the cell 2. Chromosomes line up along the center of the cell 3. kinetochore fibers hold chromosomes in place Anaphase 1. Chromatids separate at the centromere 2. Chromatids move, centromere first, toward opposite poles 3. Chromatids are considered to be individual chromosomes after separation. One chromosome (unduplicated) one chromatid two sister chromatids one chromatid One chromosome (duplicated) Telophase and Cytokinesis 1. Centrioles and spindle fibers disappear 2. chromosomes unwind into chromatin “spaghetti” 3. nuclear membrane forms around set of chromatin and the nucleolus appears 4. Cytoplasm divides (cytokinesis), forming two new cells 5. Organelles are separated into two new cells Control of Cell Division • signals from the cell can trigger the next phase of the cell cycle • 3 checkpoints: – Cell growth (G1) checkpoint • decide whether cell should divide or not. – Yes - cell begins G2 phase – No - cell goes into G0 phase – DNA synthesis (G2) checkpoint • signal the cell to enter mitosis – Mitosis checkpoint • signal the cell to exit mitosis Application 1. Growth 2. Self Healing 3. Cancer - uncontrolled growth of cells - error at G1 checkpoint Which stage? Mitosis • http://www.biologycorner.com/flash/mitosis .html Mitosis vs. Meiosis MEIOSIS – Takes place in two sets of divisions, meiosis I and meiosis II – Occurs in Germ cells found in the ovaries and testes • Meiosis I – Reduces the number of chromosomes from diploid to haploid • Meiosis II – Produces four haploid daughter cells http://www.johnkyrk.com/meiosis.html Prophase I • Like Mitosis: –DNA is coiled into chromosomes –Spindle fibers appear –Nucleolus and nuclear membrane disassemble • Different than Mitosis • Synapsis - homologous chromosomes pair up • Crossing over - exchange genetic information, or genetic recombination Meiosis I continued Metaphase I: tetrads line up at the nucleus tetrad – a pair of homologous chromosomes Anaphase I: Independent assortment - tetrads move to opposite sides of the cell (random) Telophase I and Cytokinesis: chromosomes reach opposite sides of the cell and the cell divides Meiosis II - Begins with the two cells Meiosis I formed in Meiosis I - DNA is NOT copied before Meiosis II Prophase II, Metaphase II, and Anaphase II – similar to Meiosis I, but each half receives only half of the genetic information Telophase II and Cytokinesis II - Like Meiosis I Meiosis II - Ends with four cells instead of two - Cells are haploid instead of diploid Gametes • In animals, gametes are the only cells that use meiosis. • Spermatogenesis – produces 4 sperm cells • Oogenesis – produces 1 egg cell, or ovum, and three polar bodies, which degenerate. What is crossing over? Crossing over occurs when pieces of chromatids break off and attach to the homologous chromosome by it. What are some key differences and similarities between mitosis and meiosis? • Mitosis is used by regular cells, meiosis is used by reproductive cells • There is one division in Mitosis, and two divisions in Meiosis • Mitosis ends with two diploid cells, Meiosis ends up with four haploid cells • In both Mitosis and Meiosis DNA is doubled just once.
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