Transcript here
Unit 6 DNA & The Cell Cycle Test date 11-18 GENETIC MATERIAL In the middle of the 1900’s scientists were asking questions about genes. What is a gene made of? How do genes work? How do genes determine characteristics of organisms? DO PROTEINS CARRY THE GENETIC CODE? At the time most scientists believed that proteins _________ had to be the molecules that made up genes. There were so many different kinds proteins and DNA seemed to be too monotonous . . . repeating the same ___ 4 subunits. SEE GRIFFITH’s EXPERIMENT 1928 – Frederick Griffith looked at pneumonia bacteria trying to figure out what made people die S (SMOOTH) strain - killed mice R (Rough) strain -mice lived Images from: http://microvet.arizona.edu/Courses/vsc610/mic205/griffith.jpg If he heated the LETHAL strain first _______________ . . . mice lived. The heat killed bacteria were no longer LETHAL. Heat killed + live rough = dead mouse Images from: http://microvet.arizona.edu/Courses/vsc610/mic205/griffith.jpg Griffith called this process TRANSFORMATION because one strain of __________________ bacteria had been changed permanently into another. But what was the factor that caused the transformation? A protein ? A lipid ? A carbohydrate ? A nucleic acid ? Griffith 1928 (British) Studied: Better way to fight pneumonia Experiments: Smooth bacteria=dead mouse. Rough bacteria = alive mouse. Heat killed smooth= live mouse Heat killed smooth + rough=Dead mouse Conclusions: Some molecules or group of molecules changed the harmless rough bacteria into deadly smooth bacteria. Called transformation http://en.wikipedia.org/wiki/Oswald_Avery 1944Oswald Avery’s team of scientists repeat Griffith’s experiments looking for the transforming molecule. After heat killing the LETHAL Pneumonia bacteria, he treated them with digestive enzymes that destroy specific kinds of molecules. If proteins, polysaccharides, lipids, or RNA’s were destroyed .. . Transformation still occurred! ______________________________ http://cystitis-cystitis.com/Images/testtube.jpg http://faculty.uca.edu/~johnc/mbi1440.htm But when they treated the heat-killed LETHAL bacteria with enzymes to destroy _____ there was NO DNA transformation! . . . the mice lived! DNA was the molecule that caused the genetic change. http://web.jjay.cuny.edu/~acarpi/NSC/12-dna.htm GRIFFITH EXPERIMENT (PNEUMONIA-RAT) Showed genetic ____________ material could be passed between bacteria & cause a change. AVERY EXPERIMENT (Digestive enzymes) showed that the genetic material DNA was _____ Avery 1944 Studying: Process of transformation as a key to finding heredity Experiments: Repeated above experiment: Treated heat-killed smooth with enzymes that destroyed either proteins, lipids, carbohydrates, RNA. None affected transformation. When DNA was destroyed transformation was blocked. Conclusions: Genes are made of DNA Scientists are skeptical… it takes more than one experiment to convince them. 1952-Alfred Hershey and Martha Chase experimented with viruses that infect bacteria = _________________ bacteriophages Knew bacteriophages were made of proteins and _______ DNA ________ Hear about their cool experiment http://www.mun.ca/biology/scarr/Chase_&_Hershey_1953.jpg http://www.mun.ca/biology/scarr/hersheychase-experiment.jpg HERSHEY-CHASE BLENDER EXPERIMENT only DNA not protein Showed_______________ entered cell during infection. Conclusion: Genetic material ______________in virus was DNA _____ not protein BACTERIAL VIRUSES http://faculty.uca.edu/~johnc/mbi1440.htm Hershey & Chase 1950 Studying: Skeptical of Avery’s conclusion. Wanted more support Experiments: Bacteriophage- virus infects bacteria. Knew viruses made of protein & DNA. Used radioactive isotopes to mark them Protein-sulfur-35, DNAphosphorus-32 Found phosphorus-32 in bacteria Conclusions: Genetic material is DNA, not protein Chargaff 1950 Studying: Studied nucleotide composition in DNA Experiments: Showed that there was the same amount of adenine & thymine, and cytosine & guanine Conclusions: Chargaff’s rule: Always!! A-T C-G (Ash Tray / Garbage Can) DNA is a DOUBLE HELIX http://www.time.com/time/time100/scientist/profile/watsoncrick.html http://en.wikipedia.org/wiki/Rosalind_Franklin X-ray experiments by Rosalind Franklin led James Watson and Francis Crick to the discovery of the structure of DNA in 1953 Franklin 1951 Studying: Studied DNA using x-ray diffraction Experiments: Powerful x-ray beams is aimed at a sample, ten the scattering pattern of the x-ray is recorded on the film Conclusions: By itself does not reveal the structure of DNA SHE WAS CHEATED OUT OF THE PRIZE!!! Watson & Crick 1953 Studying: What is the structure of DNA? What held the two strands together? Experiments: Analyzed other scientists’ work. Few weeks after Franklin’s x-ray experiments- they solved the puzzle of the structure of DNA. Made sketches & built models Conclusions: Two strands twisted around one another Double Helix Hydrogen bonds between the bases DNA REPLICATION Prior to cell division the _________, replicate DNA must ______. DNA can replicate itself exactly due to Chargaff’s rules ___________ Replication occurs in nucleus the ________of the cell and requires the participation of several _________. enzymes Summary of DNA Replication helicase 1. Enzyme _______“unzips” DNA by breaking hydrogen bonds between the _________ nitrogen bases the______________. Where unzipping begins is called origin of replication the__________________; the continuation replication fork of unzipping is the ______________, Occurs chromosome in several places in each _____________; broken zipper like a ______________ binding proteins hold the 2. Single-strand __________________________ separated DNA strands apart. Summary of DNA Replication DNA polymerase adds nucleotides to 3. ______________ both sides of the DNA molecule according to base pairing rules. DNA polymerase has two restrictions: 5’ – 3’ a. it can only add nucleotides in a ______ direction b. it can only add nucleotides to an existing strand. Summary of DNA Replication 4. Two sides of DNA are replicated differently because nucleotides can only be added in a _____________ 5’ – 3’ direction _____________side replicated in the Leading strand same direction as the replication fork. ____________ __________ are moved in by DNA Nucleotides polymerase in a 5’ – 3’ direction as the DNA is unzipped. Summary of DNA Replication Lagging strand ____________- nucleotides are __________ added away from the replication fork. Short segments ______________ of nucleotides are synthesized, as the DNA is unzipped. These short segments are known as Okazaki fragments _______________. Eventually, the ____________ enzyme ligase “glues” together the Okazaki fragments ________________to create a continuous strand of nucleotides Summary of DNA Replication 5. Another type of DNA polymerase proofreads the replicated DNA to _________ minimize the change of ________. mutation ________ two identical DNA molecules, 6. Results in ___________ each consisting of one _______ original strand and new strand. one ____ Summary of DNA Replication These two identical DNA molecules are the ______________ sister chromatids that proceed through _______ mitosis Once replication has been completed, the cell moves into ___ G2 and then, prophase of mitosis _________________. Cellular Growth The third statement of the Cell Theory states that all cells come from ______________. pre-existing cell 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 cell cycle division is known as the __________. Cellular Growth The cell cycle is defined as the period of cell division to time from the beginning of ___________ the _____________________. This type beginning of the next asexual reproduction. of cell division is ________ In asexual reproduction, the genome or DNA of the cell is exactly replicated _____ 2 identical cells resulting in ________________. I. IMPORTANCE OF ASEXUAL REPRODUCTION A. Single-celled Organisms Single-celled organisms like bacteria & yeast use asexual _______________ reproduction to ______________________________ make new organisms-reproduce I. IMPORTANCE OF ASEXUAL REPRODUCTION B. Multicellular Organisms 1. Growth & Development – Organisms division rather than grow through cell ___________, unlimited growth of a cell because if a cell gets too large, it cannot meet its own homeostasis needs and maintain ____________. A cell grows to a certain size, and then it divides. 2. Renewal & Repair – Cell division is used to replace cells that die from normal wear & tear; for example, __________. Other types skin cells of cells maintain the ability to divide, but keep it in reserve unless severely damaged; for liver cells Other cells do not example, __________. appear to divide at all in a mature human; for nerve cells, cardiac muscle cells example, ____________________________, although recent experimental findings appear theory to dispute this long-standing _______. II. Cell Size Limitations Ratio of surface are to volume- As the cytoplasm cell grows, its volume (__________) increases much more rapidly than the cell membrane surface area (______________). The cell will have difficulty supplying nutrients & expelling enough waste ___________________ products. By remaining small, cells have a higher ratio of surface area to volume _______ and can sustain themselves more easily. Surface Area (length x width x 6) Volume (length x width x height) Ratio of Surface Area to Volume Transport of substances- movement of substances within the cell managed more easily in a small cell vs. a large. 1. _________Diffusion diffusion over long distances is slow & inefficient because it relies on random movement cytoskeleton Motor Proteins ____________ 2. ______________transportation network becomes less efficient for a cell if the distance to travel becomes too large. Cellular Communications- Cell size affects the ability of the cell to communicate ____________ instructions for cellular functions; if too large it becomes __________ impossible for cellular communications. Ex. The signals that trigger protein synthesis might not reach the _____________ ribosome fast enough for protein synthesis to occur. CELL CYCLE IN PROKARYOTES (p. 252 & 520) bacteria undergo a type of cell division All ________ binary fission known as _____________. Binary fission is a less complex, faster process than eukaryotic cell division because bacteria lack a nucleus, membrane bound organelles and ______________________________ 1 chromosome. have only __ The Cell Cycle G1 Phase- (Gap 1) Cell is growing, carrying out normal cell functions & preparing to replicate DNA S phase- synthesis- the period when a cell copies its DNA in preparation for cell division G2 phase- (Gap 2) Cell is preparing for cell division *Producing microtubules *Taking inventory M phase- Mitosis The Cell Cycle Interphase Cell grows & carries out normal cell process DNA replicates Prophase Nuclear membrane disintegrates Nucleolus disappears Chromosomes condense Spindle apparatus begins to form between the poles Metaphase Chromosome s attach to spindle apparatus & align along the equator of cell Anaphase Microtubules shorten, moving chromosome s to opposite poles Telophase Chromosomes reach poles of cells Nuclear envelope reforms Nucleolus reappears Chromosomes decondense Cytokinesis Plant cell: Cell plate forms dividing daughters Animal cells: Cleavage furrow forms at equator of cell & pinches inward until cell divides in two Normal Cell Cycle The timing & rate of cell division are important to the health of an organism. The _________ rate of cell division varies depending on the type of cell A. Cyclins (__________) & cyclin-dependent proteins kinases (____________) (CDKs)- bind to each enzymes other to start various activities of the cell cycle. Ex. Signal start of cell cycle, DNA replication protein synthesis, nuclear ________________, division & end of the ____________( different Cell cycle _____________for each) combination Normal Cell Cycle checkpoints B. _____________cell cycle built in checkpoints that __________ monitors the cycle & can stop it if something goes wrong. a. Checkpoint near end of G1 monitors DNA damage for _____________& can stop the cycle before entering the S stage, Quality control b. ________________checkpoints during S phase & after Spindle checkpoints c. _____________________if problem with spindle can stop before ____________ cytokinesis Abnormal Cell Cycle: Cancer (page 11 of booklet) cancer ______________ is the uncontrolled growth & division of cells- a failure in the regulation of the cell cycle. Causes of Cancer mutations Cellular- ________ occurs is not repaired by cell. cancer can result. Carcinogenssubstances & ___________ agents that are know to cause cancer. Include: tobacco, UV rays Genetics Biological agentsBacteria & viruses __________________ Apoptosis- (page 11 of booklet) Programmed cell _____________ death. Cell going through will shrink & shrivel in a controlled process. Ex. During development of human Hand and foot _____________________ webbing ____ Plants- localized death of cells results in leaves falling in autumn Cells damaged beyond repair Stem Cells/PluripotentPage 11 of booklet Stem cells or pluripotent cellsunspecialized are __________ cells that can develop into specialized _____________ cells with the signals proper ________ 2 types ___________ embryonic stem cells adult ___________ stem cells