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Cell Reproduction 1 The Cell Cycle 2 start Division of everything else P, M, A, T Division of nucleus 3 The Cell Cycle Fig. 8.4, p. 130 Cell Cycle • Cycle starts when a new cell forms • Has 3 stages of CELL CYCLE – Interphase G1, S, G2 – Mitosis phase (dividing of nucleus) thru p,m,a,t – Cytokinesis division of everything else from cell 3 easy steps to divide a bacteria …(prokaryotic cells).. BINARY FISSION: • 1. chromosomes make copies • 2. cell grows til about 2x its size! • 3. cell membrane forms in between the copied chromosomes and the cell SPLiTS! Cell Division in Prokaryotes Parent cell Chromosome replicates Cell splits 2 identical daughter cells 7 1) 2) 3) If a fishes sperm cell has 12 chromosomes, how many chromosomes does his scale cells have? _____ Your chromosomes look like a ______ and bacteria’s chromosome looks like a _____. Heredity information for most traits is generally located in a. b. c. d. 4) Chromosomes found on genes The ribosome of sperm cells The mitochondria in the cytoplasm Genes found on chromosomes Compared to the number of chromosomes in a normal autosomal (body) cell, the number of chromosomes in a sperm (sex) cell is a. b. The same Twice as great c. four times greater d.half 5) Which process is trying to stop global warming? a. deforestation b. combustion c. photosynthesis d. industrialization B. Mitosis Mitotic Phase (Nucleus Divides) 2nd phase of cell cycle …remember • Four stages: Prophase Metaphase Anaphase Telophase Early Prophase (interphase) spindle starts forming Chromatin starts to coil Chromosomes 10 Prophase Nuclear membrane breaks down chromatin coils into duplicated chromosomes (X’s) Kinetochores form Spindle fibers form Centrioles start moving to opposite sides Metaphase Spindle fibers attach to the kinetochores and the Chromosomes move to the MIDDLE, line up single file (center, equator of the cell) (a line of 46 chromosomes long) Equator of Cell Pole of the Cell 12 Anaphase (break apart) • Chromatids (half of an X) are pulled apart (separate) – Now each side has the same copy of DNA • Cell elongates Telophase • Chromatids uncoil to chromatin • Spindle fibers go away • Nuclear membranes start to form • Cell continues to get bigger Starts to look like Two cells (Opposite of Prophase) Cytokinesis Division of the cell into 2 In plant cells, cell plate forms at the equator to divide cell In animal cells, cleavage furrow forms to split cell 16 2) Animal Cell Division Results of Mitosis • 2 cells with identical DNA (diploid #) • Chromosomes in unduplicated form • Cell CYCLE STARTS OVER AGAIN…G1 Name the Mitotic Stages: Interphase Name this? Prophase Telophase Name this? Metaphase Anaphase 19 1) What are the 3 phases of the cell cycle? 2) What can interphase be broken down into? 3) What happens during the S phase? 4) What does mitosis mean? What cells do this process? 5) What does cytokinesis mean? 6) How many cells will there be by the end of the cell cycle if we started with 1 cell? 7) Who does binary fission? LETS TALK ABOUT SEX!!!!!! CELLS…..Got ur attention now huh???? Meiosis only in sex cells (haploid) • Occurs here is men = testes that produces sperm • And here in women = ovaries that produces eggs – EGG & SPERM cells have half the # of chromosomes!....they have 23 chromosomes each (n)…when they come together…(2n) Meiosis: One Replication and Two Divisions(PMAT 1 and PMAT 2…ex:P1, A2) Mitosis: One Replication and One Division* (just PMAT) • Meiosis: 4 haploid nuclei form (because 2 divisions) • Mitosis: 2 diploid nuclei form (because 1 division) Early Prophase (interphase) spindle starts forming Chromatin starts to coil Chromosomes 25 Prophase I Homologs pair up called synapsis (mom chrom #1 pairs with dad chrom #1 Crossing over occurs Chromatin coils to chromosomes (x’s). Spindle forms. Nuclear membrane breaks. Centrioles move to opposite poles 26 Homologous Chromosomes Carry same Genes..different alleles (form of a gene) • Cell has two of each chromosome, One chromosome in each pair from mother, other from father brown blue Mom’s Dad’s Crossing-Over Homologs cross over and genes are exchanged……produces genetic diversity (makes each cell genetically different) 28 Metaphase I • Homologs meet in the Middle, lining up in their PAIRS (double file, 23 long) • Random assortment of chromosomes …..not all of mommies on one side… Anaphase I • *Homolog pairs* break apart • Go back as a whole duplicated chromosome (X’s) Telophase I • Nuclear membranes reform • Spindle fibers go away • Cell elongates • Cytokinesis spilt of cytoplasm to form 2 cells each with haploid # (23), but chromosomes are still duplicated • Chromosomes do not uncoil ANSWER 1) When does crossing over occur? 2) When does the nuclear membrane disappear? 3) When does chromatids separate (break apart)? 4) When do chromosomes meet in the center? 5) How many cells end mitosis? Meiosis (2 divisions)? T/F 1) Human sperm have 23 chromosomes 2) Cell division in bacteria(prokaryote) is binary fission 3) Mitosis is the process by which the nucleus divides 4) After interphase comes cytokinesis 5) DNA is replicated in the G1 phase 6) Chromatin coils up during anaphase Meiosis II: Reducing Chromosome Number Prophase II Metaphase Telophase II Anaphase 4 Genetically II II Different haploid cells 33 Prophase II • Centrioles move to opposite poles • Nuclear membrane goes away • Spindle fibers form Metaphase II • 23 Duplicated chromosomes meet in the middle (single file) Anaphase II • chromatids separate (break apart) Telophase II • • • • Spindle fibers disappear Chromosomes uncoil to chromatin Nuclear membrane forms Cytokinesis occurs producing Four HAPLOID cells…THAT ARE ALL GENETICALLY DIFFERENT Comparison of Divisions Mitosis Meiosis 2 Number of divisions 1 Number of daughter cells 2 4 Genetically identical? Yes No Chromosome # 46 23 Where body cells Sex cells When Throughout life At sexual maturity Growth and repair Sexual reproduction Role 38 Gametogenesis Oogenesis or Spermatogenesis 39 Oogenesis making of eggs through meiosis Occurs in the ovaries produce 3 polar bodies that die (smaller) and 1 oocyte (immature egg that is bigger) will turn into an egg (ovum) Starting at puberty, one oocyte matures into an ovum (egg) every 28 days Find the: ovum & polar bodies Spermatogenesis= making sperm Occurs in the testes produce 4 spermatids (baby sperm without tails) Spermatids mature into sperm…grow tail Men produce about 250 million sperm per day…..only 1 will win 42 spermatogonium (diploid ) primary spermatocyte (diploid) secondary spermatocytes (haploid) spermatids (haploid) sperm (mature, haploid male gametes) Spermatogenesis Growth Meiosis I, Cytoplasmic Division Meiosis II, Cytoplasmic Division cell differentiation, sperm formation Spermatogenesis – making sperm cells Fertilization • When sperm and egg fuse (23 +23= human 46) • 2 gametes coming together is random – Adds to variation among offspring – Remember all eggs and sperm are different from each other, this is why u don’t look exactly like your siblings. TWINS • Fraternal Twins look different – 2 eggs and 2 sperm……remember… all sperm and eggs are different so of course they wont look alike..can be diff sex • Identical Twins look the same – One egg and one sperm…..once fused, embryo splits….so same DNA b/c same sperm and egg…….always same sex – Conjoined twins…. starts to split….but does not finish Question If a pair of identical boy twins hooked up with a pair of identical girl twins on the same day, then they each had a child on the same day, would the babies be genetically the same (identical)? Why or why not? Things to Know: 1) 2) 3) 4) 5) 6) 7) 8) 9) All things on MP3 review for chapter 8 Cell Cycle G1 S G2 What are spindle fibers for Sexual vs asexual reproduction How twins happen….fraternal vs. identical What does the cleavage furrow do…..splits the cell into 2 Where mitosis and meiosis occurs and there phases Chromosome #’s Prokaryotic chromosomes and their division