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Unit 6 DNA and the Cell Cycle UNIT 6 - DNA & THE CELL CYCLE The third statement of the Cell Theory states that all cells come from Pre-existing cells ____________________________________. The continuity of life is based on the reproduction of cells or Cell division ____________________________. In most organisms, cells increase to a certain size and then divide into two cells. This cycle of growth and cell division is known as the Cell Cycle _________________________. Cell Cycle The cell cycle is defined as the period of time from the beginning of one Cell division _______________________________ to the ______________________________________. Beginning of the next This type of cell division is Asexual _________________ reproduction. In asexual reproduction, the genome or DNA ________________ of the cell is exactly two replicated resulting in ________ ___________________ cells. Identical I. IMPORTANCE OF ASEXUAL REPRODUCTION (p. 241-243) A. Single-celled Organisms Single-celled organisms belonging to Protista kingdoms ___________________, Archaebacteria ______________________, Eubacteria _______________, and Fungi ____________, use asexual reproduction Make new organisms-Reproduce to______________________________. B. Multicellular Organisms 1. Growth & Development – Organisms grow Cell division through ___________________________, rather than unlimited growth of a cell. Surface Area to Volume Ratio – As the size of volume an object increases, the __________________ increases at a much faster rate than the Surface area _____________________; therefore, the surface area to volume ratio becomes a ______________ number. Decreasing Surface Area to Volume In a cell, the Cell membrane ________________________ represents the surface area and the cytoplasm ________________________ represents the volume. At a certain point, a cell can no longer meet its needs and maintain homeostasis _____________________; therefore, cells only grow to a certain size. 2. Renewal & Repair – Cell division is used to replace cells that die from normal wear & tear; for example, Digestive cells Skin cells ________________ and __________________. Other types of cells maintain the ability to divide, but keep it in reserve unless severely damaged; Liver cells for example, ___________________________. Other cells do not appear to divide at all in a mature human; for example, Nerve cells ____________________ and Cardiac muscle cells (heart) __________________________. II. CELL CYCLE IN PROKARYOTES (p. 475) bacteria All ______________ undergo a type of cell division known as Binary fission _______________________. Binary fission is a less complex, faster process than eukaryotic cell division because nucleus bacteria lack a _________, Membrane bound organelles ______________________________ and One (1) have only ________chromosome Binary Fission Pinching in III. CELL CYCLE IN EUKARYOTES - AN OVERVIEW (p. 245) There are two main parts to the eukaryotic cell cycle: 90% A. Interphase - Accounts for about ________ of cell cycle. This is the period of time in which a Normal activities and doing its cell job cell is carrying out _______________________. Protein __________________ synthesis is occurring at a high rate. The cell’s DNA is in the form of chromatin _______________, long, fine strands of DNA protein wrapped in ______________. M-Phase B. M-Phase – Period of time in which cell division occurs. Consists of two main events: Mitosis – Division of the nucleus ____________________________ Cytokinesis – Division of the cytoplasm _________________________ IV. A CLOSER LOOK AT INTERPHASE There are three stages to interphase: grows G1 - Cell ______________, carries out normal cell activities such as Protein synthesis and cellular respiration _________________________________________. Period in which _____________ production is highest Protein DNA Synthesis S - ______________. Replication of ___________; known as the “_________________________”. Point of No Return Replication takes place in the _____________________ nucleus of the cell. Mitosis G2 - Preparation for _____________________. All organelles ______________________ are replicated in ____________________ cells. eukaryotic At the end of interphase . . . Cell Membrane Centrioles (replicated) DNA has been replicated – a. _____ still in chromatin form. centrioles b. ____________ have been replicated in __________ cells animal only. This replication results in 2 pairs of centrioles, microtubules composed of ______________. _nuclear envelope_ c. The __________________ and nucleolus _________are still present. Protein microtubules that will form spindle fibers nucleolus Chromatin Nuclear envelope V. A CLOSER LOOK AT MITOSIS (pp. 246-248) Mitosis, also known as the _M - Phase_, is described in four stages, but it is a continuous process. A. PROPHASE – In prophase, the nucleus is preparing to divide. This includes . . . A. Prophase –The longest phase of mitosis Microtubules form Spindle fibers Sister chromatids Nucleolus attach at the 1.______________________ and Nuclear envelope centromere ___________ _____________ disassemble. DNA 2.Replicated ___________ thickens & condenses results in ______________ made up of 2 chromosomes Sister chromatids ________________ ______ held together at the __________________ centromere Centrioles 3.________________begin moving to opposite poles of the cell. Microtubules 4. _______________________ form Spindle fibers ____________________________. Specific spindle fibers attach to the sister chromatids at the centromere ______________________. Centrioles Nuclear envelope disintegrates B. METAPHASE-Shortest phase In metaphase, the sister chromatids are Middle or center or equator organized in the ___________________ of the cell. Metaphase centrioles Kinetochore microtubules Spindle fiber network Sister chromatids Spindle fiber 1._____________________ network is fully formed with centrioles ________________ at opposite ends. 2.Each Sister chromatid _______________________is attached to a spindle fiber at kinetochore the _______________ located at the centromere ________________________ 3.Sister chromatids align at equator the _______________ of the cell. C. ANAPHASE In anaphase, the sister chromatids are apart pulled______. Anaphase Centrioles Kinetochore microtubules Non-kinetochore microtubules Centromeres 1.________________ split. 2.Sister _____________ are chromatids pulled apart by kinetochore microtubules _______________________; move to opposite ends of the cell. 3.Genetic material is now known as daughter chromosomes _______________________. 4.Cell elongates; prepares for two new nuclei. D. Telophase By the end of telophase… Telophase separate 1.Complete and _____________________ set of chromosomes _____________ at each pole of the cell. Spindle fibers 2.__________________disassemble. Nuclear envelope 3.New _______________________forms around each group of chromosomes. chromatin 4.DNA uncoils _____________________ 5.________________ reforms nucleolus ribosomes ___________________ are produced Protein synthesis resumes cell _______________ ________________________ Metabolic activity resumes Chromosomes Pinching in Nuclear envelope reforms E. CYTOKINESIS This refers to the actual division of the cytoplasm ____________________. Cytokinesis begins during telophase ______________ and differs in plant versus animal cells cell wall because plant cells have a _____________. 1. Animal Cell – In the final stages of telophase, the cell membrane _______________ pinches in. This is referred to as a __________________ and is due to the action of Cleavage furrow ____________________. Invagination w/microfilaments(actin) This cleavage furrow deepens until the parent cell is pinched in two, producing two separate, _________ daughter cells. identical Plant Cell Cytokinesis 2. Plant Cell – There is no cleavage furrow in plant cells. Instead, during late vesicles telophase, _______ from the Golgi apparatus _________________ move to the center cellulose of the cell where _____________and other materials they contain come together cell plate which eventually to form a_______, cell wall develops into a ____________. CYTOKINESIS Cell wall Cleavage furrow Daughter cells Animal Cell Vesicles Containing Cellulose Plant Cell New cell wall Cell plate New cell Walls around New daughter Cells Control of the Cell Cycle VI. CONTROL OF THE CELL CYCLE (pp. 250-253) A. Timing of the Cell Cycle The timing of the cell cycle is regulated by cyclins proteins known as _____________ that bind with enzymes known as kinases ________________ to form a complex called ___________________________ Cyclin-dependent kinases or ___________. These ____________ CDKs enzymes are responsible for monitoring checkpoints in the cell cycle. Cell Cycle If the progression of the cell cycle is too dying cells are not replaced slow, ___________________________. Cell Cycle If the cell cycle progresses too quickly, the result is uncontrolled cell growth or _________. This is harmful for many cancer reasons If a cell spends all of its time dividing, It is not doing its cell job _____________________ Cell Cycle The rapidly- dividing, nonfunctional cells steal nutrients ___________________ from healthy, them to die functioning cells causing ___________. The rapid replication of DNA ____ results in a greater mutations risk of ___________. B. Stem Cells B. Stem Cells undifferentiated cells that Stem cells are ____________ have the ability to _____________. reproduce forever Stem cells that can give rise to many types of pluripotent cells are said to be _________. Stem Cells Although stem cells are found in certain locations in adults, most research involves embryonic the use of ____________ stem cells, due to the fact they are considered to be immortal “___________” and capable of unlimited specialization. Scientists hope that stem cells may be used as implants to replace ______________________________, but Damaged tissues and organs legal there are many _______ and __________ ethical concerns. C. Number of Cell Division per Cell Each cell is programmed to divide a certain number of times, and then it will not divide again. This is monitored by telomeres a series of DNA ________ nucleotides ________, found at the tips of each __________. chromosome Number of Cell Divisions per Cell S of the cell cycle, As DNA is replicated __________ in __ the telomeres shorten. Once they reach a critical length, the DNA does not replicate again, and the cell does not _______________. divide ________________ and _____________ Cancer cells stem cells produce an enzyme known as _____________, telomerase which restores the chromosomes back to their original length, thereby theoretically making the cell capable of ______________ cell division. unlimited A CLOSER LOOK AT DNA & REPLICATION I. DNA – THE DISCOVERY OF THE MOLECULE OF INHERITANCE (pp. 287-294) DNA contains the ________________ Genetic code and the _______________________________ for a cell. Working instructions Scientists in the early 1900s realized that inheritance was dependent on __________ found on genes chromosomes ____________________ and that chromosomes were DNA composed of ___________ and __________________. protein It wasn’t until the 1940s that scientists established _______ DNA as the molecule of inheritance, and still another 15 years passed before the structure of DNA was discovered. A. Griffith (1928) Discovered that bacteria can take up genetic material from environment in a process known transformation as _____________________. Performed experiments with _____________ mice Pneumococcus and bacteria known as ___________________. Mixed harmless living bacteria with dead ______________________ Pathogenic (deadly) bacteria and injected them into mice. Mice died. Griffith’s Experiment B. Avery, et.al. (1944) Set up experiments to identify “transforming substance” discovered by Griffith Used enzymes that destroyed carbohydrates, lipids, proteins, and RNA . . . transformation still occurred. Used an enzyme that destroyed DNA, Transformation did not occur, mice survived _________________________________. DNA Concluded that ______ stores and transmits the genetic information from one generation of an organism to the next. Scientific community did not completely accept their conclusion Avery’s Experiment C. Hershey & Chase (1952) bacteriophagewhich Used a virus known as a ____________ bacteria infects _________. DNA protein Viruses are composed of _______and ____________; host cell in order to replicate. require a ______ Hershey & Chase recognized that virus must inject its genetic material into the bacterial cell for replication to take place. isotopes Used labeled ________ to determine whether DNA or protein was injected into bacterium. Hershey & Chase concluded that the genetic material of DNA the bacteriophage was ________________. Hershey and Chase’s Experiment D. Watson & Crick (1953) Used molecular models to solve the 3dimensional structure of DNA “Borrowed” an x-ray of DNA taken by Rosalind Franklin to solve the puzzle ________________ Double Helix Proposed a ______________ structure with a deoxyribose backbone of alternating ________________ and phosphate Nitrogen bases ______________with ____________________ paired in the middle Rosalind Franklin Died at age 37 from cancer, probably caused by all her exposure to radiation from the x-ray diffraction technique. Did not receive the Nobel Prize. Watson and Crick (Won Nobel Prize) Facts I would want to know! II. STRUCTURE OF DNA Slide 51 Deoxyribonucleic acidis a ________ Nucleic acid made up ______________ nucleotide monomers. Each DNA of _________ nucleotide is composed of: _______ Deoxyribose (5-carbon sugar) _________________________ Phosphate group _________________________ Nitrogen Base _________________________ Structure of DNA covalent bonds hold the Strong, stable ________ components of each nucleotide together. covalent In addition, nucleotides form strong __________ bonds with other nucleotides, resulting in a long strand of nucleotides. hydrogen bonding Double helix created by ________ Nitrogen bases between ________________________ The diameter of DNA is uniform due to specific pairing of nitrogen bases Structure of DNA Purines – double-ringed nitrogen bases guanine ____________ adenine ____________ Pyrimidines - single-ringed nitrogen bases cytosine ___________ thymine ___________ (And Uracil) Purines and Pyrimidines Purines __________ always base pairs with a pyrimidine ____________, specifically … thymine Adenine _______________ base pairs with ______________ cytosine Guanine _______________ base pairs with ______________ Structure of DNA Watson Crick ________ and ________ determined this diameter structurally because the ___________ of DNA is uniform. Chargaff ___________ determined this chemically. His chemical analysis of DNA from many different organisms always showed that the % of thymineand the % of guanine adenine = % ________ cytosine = the % _________. These findings are Chargaff’s rules known as ______________. Structure of DNA The two strands of nucleotides are Anti-parallel that is, they run opposite to __________; each other. Pattern and _______ number of It is the _______ nucleotides that makes each gene unique. Deoxyribonucleic Acid adenine covalent bond cytosine deoxyribose guanine hydrogen bond nitrogen bases nucleotide phosphate group purines pyrimidines thymine 5’ end 3’ end III. DNA REPLICATION (pp. 295-299) Cell division Prior to ___________, the DNA must __________________. replicate This occurs in __ S of interphase _____________________. During this part of the cell cycle, DNA is in the chromatin form of ______________. DNA can replicate Chargaff’s base pairing rules itself exactly due to _____________________. nucleus Replication occurs in the _________ of the cell and requires the participation of enzymes several _____________________. Replication may be summarized in the following steps: Helicase DNA is “unzipped” by the enzyme, __________. hydrogen Helicase breaks the ______________________ Nitrogen bases bonds between the _____________________. The point where the unzipping begins is known Origin of replication as the ____________________________. The continuation of the unzipping is called the Replication fork _________________________________. This occurs in several places in each chromosome __________________, much like a Broken zipper __________________________________. DNA Replication Single stranded binding proteins _________________________________ hold the separated DNA strands apart. topoisomerase Another enzyme, ___________________ helicase moves ahead of the _________________ to relieve tension in the double helix as it is being unzipped. Topoisomerase DNA Replication DNA polymerase The enzyme, ________________ adds nucleotides to both sides of the DNA molecule according to Base-pairing rules _________________________ rules; however, DNA polymerase has two restrictions: 5’ – 3’ It can only add nucleotides in a __________ direction. It can only add nucleotides to an existing strand. Before DNA polymerase begins moving in nucleotides, RNA Primer an __________ ________________ must be put in place. Eventually this primer is removed and replaced with DNA nucleotides. DNA Replication The two sides of the DNA molecule are replicated differently because nucleotides can 5’ – 3’ direction: only be added in a ______ One side of the DNA molecule is being replicated in the Replication fork same direction as the __________________________. leading This is known as the _______________________ strand. Nucleotides are moved in by DNA polymerase 5’ – 3’ _____________________ in a _______________ direction as the DNA is unzipped. Okazaki Fragments On the other side of the DNA molecule, nucleotides are added away ________________ from the replication fork. This is known as Lagging the _____________________ strand. Short segments of nucleotides are synthesized, each with a new RNA primer _____________________, as the DNA is unzipped. These short Okazaki ________. fragments segments are known as ________________ ligase Eventually, another enzyme known as __________________ Okazaki “glues” together the _____________ fragments to create a continuous strand of nucleotides. DNA polymerase Another type of _________________ proofreads the mutation replicated DNA to minimize the chance of ___________. Okazaki Fragment Replication Fork DNA Replication identical The result is two ____________DNA molecules, each new DNA consists of one original _________________ strand and one new strand. This is known as the ________ ________________ Semi-conservative model of replication. These two identical DNA molecules are the Sister chromatids ____________________ that proceed through mitosis ______. Once replication has been completed, the cell G2 and then, ________________ prophase moves into ___ of mitosis ________________.