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Figure 12–2 Griffith’s Experiment Section 12-1 Heat-killed, disease-causing bacteria (smooth colonies) Disease-causing bacteria (smooth colonies) Harmless bacteria Heat-killed, disease(rough colonies) causing bacteria (smooth colonies) Dies of pneumonia Go to Section: Lives Lives Control (no growth) Harmless bacteria (rough colonies) Dies of pneumonia Live, disease-causing bacteria (smooth colonies) Figure 12–2 Griffith’s Experiment Section 12-1 Heat-killed, disease-causing bacteria (smooth colonies) Disease-causing bacteria (smooth colonies) Harmless bacteria Heat-killed, disease(rough colonies) causing bacteria (smooth colonies) Dies of pneumonia Go to Section: Lives Lives Control (no growth) Harmless bacteria (rough colonies) Dies of pneumonia Live, disease-causing bacteria (smooth colonies) Avery and Colleagues • 1944 • Let’s repeat Griffith’s work! • But which molecule is involved in the transformation? • Was the “gene” a carbohydrate, lipid, protein, RNA or DNA? Figure 12–4 Hershey-Chase Experiment Section 12-1 Go to Section: Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium Figure 12–4 Hershey-Chase Experiment Section 12-1 Go to Section: Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium Figure 12–4 Hershey-Chase Experiment Section 12-1 Go to Section: Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium James Watson and Francis Crick Two young scientists responsible for determining the actual structure of DNA in 1953 Main Characters • • • • James Watson American 23 Has Ph.D. in Biology at very young age • Very ambitious • Wants to be famous • • • • • • Francis Crick British 35 No Ph.D. Trained as a Physicist Cavendish Lab Rosalind Franklin • British chemist who used x-ray diffraction technique to determine the structure of the DNA molecule • 1950’s Chromosomes and DNA The Nucleus of a cell contains chromosomes. • Chromosomes are composed of coiled DNA • DNA is composed of segments called genes • Genes determine an organisms traits Figure 12-10 Chromosome Structure of Eukaryotes Section 12-2 Chromosome Nucleosome DNA double helix Coils Supercoils Histones Go to Section: DNA Extraction • Step 1 collect your cells (chewing your cheek) • Step 2 Lyse the cells (the lysis buffer contains detergent which will break up the cell membranes) • Step 3 Remove the proteins from the DNA (the protease enzyme and the 50°C water) • Step 4 Condense the DNA (use salt and alcohol to take all the individual strands and collect them together) Figure 12–7 Structure of DNA Polymer: Nucleic Acid Section 12-1 Monomer: Nucleotide Nucleotide Hydrogen bonds Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Go to Section: Figure 12–5 DNA Nucleotides Section 12-1 Purines Adenine Guanine Phosphate group Go to Section: Pyrimidines Cytosine Thymine Deoxyribose DNA Extraction Matching • Harvest the cells • Dissolve cell membranes • Precipitate the DNA (so it is visible) • Break down the proteins • Make DNA less soluble in water (allowing it to come together) A. Gently chew the inside of your mouth and rinse with water B. Add protease (enzyme), incubate @ 50⁰C C. Mix in a detergent solution D. Add salt E. Layer cold alcohol over cell extract Section 12-1 Percentage of Bases in Four Organisms Source of DNA A T G C Streptococcus 29.8 31.6 20.5 18.0 Yeast 31.3 32.9 18.7 17.1 Herring 27.8 27.5 22.2 22.6 Human 30.9 29.4 19.9 19.8 Chargaff’s Rules Go to Section: February 28th 1953 The Eagle Pub in Cambridge, England Countdown- 3 days! • Protein Structure- wrap up/ discuss • HW Check: Read and Notes p. 47, 48 and 51-53 • Enzyme Discussion and Video • Reminder: DNA History and Structure Test Friday How is protein related to DNA? Gene Expression DNA RNA Protein Traits Review ORGANIC POLYMER Monomer Function in living things Carbohydrate Monosaccharide Energy transfer. Used in photosynthesis and cellular respiration Lipid Glycerol and Fatty Acids Major Component of cell membranes Nucleic Acid Nucleotide DNA and RNA. Used to carry genetic code. ? ? ? PROTEINS Macromolecules that contain: •Carbon •Hydrogen •Oxygen •Nitrogen Monomer: Amino Acids (20 different kinds in nature) •Amino group •Carboxyl group •R-Group Polymers: Protein; many different shapes due to the nature of the R-group Figure 2-16 Amino Acids Section 2-3 General structure Amino group Carboxyl group Alanine Go to Section: Serine Uses: •control rate of reactions (act as enzymes) •Structural molecule: formation of bones and muscles •help with transport of substances across the cell membrane •help fight disease (many immune system molecules are proteins) Examples: Hemoglobin Keratin Oxytocin Proteins are the “construction workers” that build you, repair you, and make you work! Food Sources: Section 2-3 •Dairy products (yogurt, milk, cheese) •Lean meats (chicken, pork, beef) Figure 2-17 A Protein Amino acids Go to Section: What Are Enzymes? • Proteins that act as Catalyst to accelerate a chemical reaction • Not permanently changed in the process 27 Enzymes • Are specific for what they will catalyze • Are Reusable • End in –ase -Sucrase -Lactase -Maltase 28 Enzymes work by weakening bonds - they HELP the reaction happen – they DO NOT ADD ENERGY! Without Enzyme With Enzyme Free Energy Free energy of activation Reactants Products Progress of the reaction 29 Enzyme-Substrate Complex • The reactant an enzyme acts on is called the substrate Substrate Fun Fact: Substrate is another word for “reactant” Joins Enzyme 30 • The Active Site is a specific region of an enzyme molecule which binds to the substrate. Substrate Enzyme Active Site 31 Examples of enzymes at work in my body: Sucrase breaks down sucrose Lactase breaks down lactose Peptidase breaks down small proteins into amino acids DNA Helicase unwinds DNA before the process of gene copying DNA polymerase brings together nucleotides to produce new DNA 32 Answers to DNA Modeling Lab • Question 3 • Question 4 • Each original strand serves as a template to make the new strand (semi-conservative) • Complementary base pairing is used to create the new strands • DNA polymerase proofreads • To make copies of our genes • For the processes of mitosis (growth and repair) and meiosis (sexual reproduction) Chromosomes and DNA The Nucleus of a cell contains chromosomes. • Chromosomes are composed of coiled DNA • DNA is composed of segments called genes • Genes determine an organisms traits Prokaryotic Chromosome Structure Chromosome E. coli bacterium Bases on the chromosome Go to Section: Figure 12-10 Chromosome Structure of Eukaryotes Section 12-2 Chromosome Nucleosome DNA double helix Coils Supercoils Histones Go to Section: Figure 12–11 DNA Replication New strand Original strand DNA polymerase Growth DNA polymerase Growth Replication fork Replication fork New strand Go to Section: Original strand Nitrogenous bases Summary of DNA Replication 1. DNA Helicase (enzyme) “unzips” the DNA molecule. 2. Each strand serves as a template for the attachment of complementary bases 3. DNA Polymerase (enzyme) assembles a new complementary strand for each original strand of the DNA molecule 4. DNA Polymerase also proofreads the newly assembled strands DNA vs. RNA How does the code in DNA get carried out by the cell? Protein Synthesis Protein Synthesis •2- step process including Transcription and Translation Figure 12–14 Transcription Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) RNA polymerase DNA RNA Go to Section: Section 12-5 Typical Gene Structure Regulatory sites Promoter (RNA polymerase binding site) Start transcription Go to Section: DNA strand Stop transcription mRNA Editing mRNA Editing Figure 12–17 The Genetic Code Go to Section: Figure 12–18 Translation Nucleus Messenger RNA Messenger RNA is transcribed in the nucleus. Phenylalanine tRNA The mRNA then enters the cytoplasm and attaches to a ribosome. Translation begins at AUG, the start codon. Each transfer RNA has an anticodon whose bases are complementary to a codon on the mRNA strand. The ribosome positions the start codon to attract its anticodon, which is part of the tRNA that binds methionine. The ribosome also binds the next codon and its anticodon. Ribosome Go to Section: mRNA Transfer RNA Methionine mRNA Lysine Start codon Figure 12–18 Translation (continued) The Polypeptide “Assembly Line” The ribosome joins the two amino acids— methionine and phenylalanine—and breaks the bond between methionine and its tRNA. The tRNA floats away, allowing the ribosome to bind to another tRNA. The ribosome moves along the mRNA, binding new tRNA molecules and amino acids. Lysine Growing polypeptide chain Ribosome tRNA tRNA mRNA Completing the Polypeptide mRNA Ribosome Go to Section: Translation direction The process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain. Fig. 17-20 Growing polypeptides Completed polypeptide Incoming ribosomal subunits Start of mRNA (5 end) (a) End of mRNA (3 end) Ribosomes mRNA (b) 0.1 µm Concept Map Section 12-3 RNA can be Messenger RNA also called which functions to mRNA Go to Section: Ribosomal RNA Carry instructions also called which functions to rRNA Combine with proteins from to to make up DNA Ribosome Ribosomes Transfer RNA also called which functions to tRNA Bring amino acids to ribosome Central Dogma of Biology Gene Expression DNA RNA Protein Traits Mutations Example: BRAF V600E Heredity Influenced Mutations (Germline Mutations) Environmentally Influenced Mutations (Somatic Mutations) • Mistake that is present in the DNA of virtually all body cells • The mistake must occur in the reproductive cells (sperm or egg) • The mistake is copied into every body cell and can be passed to the next generation • Changes in the DNA that occur throughout the person’s life. • Mutations are only passed to the descendants of the mutated cell during cell division (mitosis) • Possible causes: Cell division mistakes, sun damage, radiations exposure, toxins, aging Case Study Mutation: Sickle Cell Anemia • Normal Hemoglobin Gene mRNA: – CCC GAA GAA AAA • Sickle Cell Hemoglobin Gene mRNA: – CCC GUU GAA AAA Mutations Gene Mutations: Substitution, Insertion, and Deletion Deletion Substitution Go to Section: Insertion Case Study Mutation: Sickle Cell Anemia • Normal Hemoglobin Gene mRNA: – CCC GAA GAA AAA – Pro Glu Glu Lys • Sickle Cell Hemoglobin Gene mRNA: – CCC GUU GAA AAA – Pro Val Glu Lys Types of Gene Mutation Figure 12–20 Chromosomal Mutations Section 12-4 Deletion Duplication Inversion Translocation Go to Section: Examples of Chromosomal Mutations • Examples of structural chromosomal abnormalities include cri du chat syndrome. Children with this syndrome have an abnormally developed larynx that makes their cry sound like the mewing of a cat in distress, as well as systemic defects. Affected children usually die in infancy. Cri du chat is caused by a deletion of a segment of DNA in chromosome 5. • A structural abnormality in chromosome 21 occurs in about 4% of people with Down syndrome. In this abnormality, a translocation, a piece of chromosome 21 breaks off during meiosis of the egg or sperm cell and attaches to chromosome 13, 14, or 22. Example Chromosomal Mutations • Down Syndrome – 47 XY or 47 XX (extra chromosome 21) • Turner Syndrome – 45 X (female missing one X) • Klinefelter Syndrome – 47 XXY (male with an extra X)