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. Chapter 11: Understanding DNA CHAPTER 11: DNA AND GENES LEARNING OBJECTIVES In addition to reading this material , you are expected to do all of the Section Assessment questions, as well as all of the Chapter 11 Assessment Questions, and the Standardized Test Practice in your textbook We will do a project related to this chapter. You will research and prepare a brief biography for one individual who contributed to our current knowledge of DNA or Heredity. This will be due on Tuesday, Feb 27. To create a class Timeline of DNA Discoveries. Be familiar with those scientists that largely contributed to discovering the structure and nature of DNA. Understand the structure of DNA, its components, bonds. Be able to describe DNA replication Be able to describe the significance of the nucleotide sequence between organisms. Be able to describe ways that nucleotide sequencing is useful to scientists and you Be Be Be Be Be able to sequence the steps in protein synthesis able to distinguish between different types of mutations able to describe the effect of genetic mutations able to describe the causes of mutations familiar with how DNA is repaired. ..\My Videos\NOVA Online Cracking the Code of Life Watch the Program Here.htm ..\..\all biology\Nova UNDERSTANDING DNA History of Research Mendel 1860’s--traits passed parent to offspring Others: set out to identify the substance responsible - Transformation Genetic material could be transferred to another organism 1928 Fredrick Griffith Discovers that Genetic material could be transferred to another organism Process by which bacteria takes up foreign DNA Non-Virulent bacteria become Virulent (disease causing) Descendents of the transformed cells also virulent. Transformation: Transformed bacteria 1.Infected with nonvirulent 2. Mice bacteria infected . with live, virulent bacteria. 3. Mice infected with heatkilled bacteria. 4.Infected with live, nonvirulent AND heatkilled bacteria. Mouse dies FROM TRANSFORMED BACTERIA . Oswald Avery (1944) Protein or DNA? *DNA is the Genetic material. Oswald Avery Protein Did vs. DNA? same type of experiments as Griffith, but treated with protein and DNAdigesting enzymes. RESULTS: Treatment with proteindigesting enzymes-- bacteria still transform Treatment with DNA-digesting enzymes-not able to transform Concluded that DNA, not protein, transforms bacteria 1952: Hershey & Chase Reconfirm DNA is the Genetic Material. They Infected bacteria with Labeled Viruses (radioisotopes of Sulfur and Phosphorous) (protein contains sulfur; DNA contains Phosphorous) virus particle labeled with 35S virus particle labeled with 32P bacterial cell (cutaway view) label outside cell label inside cell Structure of the Hereditary Material Still Was a Mystery 1953 Nobel Prize James Watson Francis Crick Maurice Wilkins Watson & Crick Developed Accurate Model Double helix shape Two strands of nucleotides Like a spiral staircase Watson-Crick Model 2 Strands of nucleotides – Sugar and phosphates covalently bonded to one another. 2 Strands held together by hydrogen bonds between bases (rungs on a ladder) Shape of a double helix Twisted The like a coiled spring. molecule coils into this – shape as a result of the – base bonding. Rosalind Franklin’s Work was Critical Expert DNA in x-ray images was some sort of helixlike a tightly coiled spring Structure DNA:polymer of nucleotides (4) Nucleotides Sugar (deoxyribose) Phosphate Nitrogen base Forms 2 long parallel chains of nucleotides covalently bonded (chains) Sugar –to -phosphate Phosphate-sugar-phosphate-sugarphosphate….. The sugars and phosphates are held together by strong covalent bonds. The bases hold the 2 strands together – The bases are held together by HYDROGEN BONDS( WEAK). – They form the “rungs” of the ladder-like shape. DNA Structure 2 strands of nucleotides Nucleotides bond (strong-covalent bonds) together to form 2 long chains Each chain connected in the middle by (weak) hydrogen bonds DNA-Made of 4 different. Nucleotides ( Nucleotides have 3 parts –1 A sugar-deoxyribose –2. Phosphate Group –3. A Base (4 kinds) – (draw and color in – your notes) 4 different nitrogeneous bases C cytosine T thymine A adenine G guanine Pattern of Base Pairing “Chargaff ‘s Rule” (1949) – Amount of adenine always equals amount of thymine and amount of guanine always equals amount of cytosine A=T and G=C Base Pairing C with G A with T ALWAYS TRUE DNA in cells Where is it found? Does it leave? Why/why not? Does a cell ever need to make more DNA? Why? When? Base Pairing or or one base pair in-text, p. 195 The Importance of Nucleotide Sequences All organisms DNA made of the same 4 bases Vary in the – Sequence of the bases – Amount of DNA The closer the relationship, the more similar the DNA sequences. Useful: – Determine evolutionary relationships – Determine whether 2 people are related – Crime scene investigation NAME:______________ DNA QUIZ 1. What is Chargoff’s rule?_____________________________________ 2. Who constructed the first accurate model of DNA?___________________________ 1. List the three parts of a DNA nucleotide 1. 2. 3. 4. Nucleotides are the ________from which the Nucleic Acid polymers DNA and RNA are Made. 5. Nucleotides link together to form 2 sides of the DNA molecule ( like 2 sides of a ladder). The sugars and phosphates are held together by strong _____________bonds. 6. The bases hold the 2 strands together. The bases are held together by weak ________________bonds. 7. Why did use radioactive phosphate in their research to confirm that DNA and not protein was the “material of transformation & inheritance”? ____________________________________________________________ 8. _______________is the process by which bacteria takes up foreign DNA 9. _________________are viruses that infect bacteria. 10. How does the DNA in YOU differ from the DNA in a tomato plant? (choose a or b) – A) in tomato plants there are different nucleotides – B) In tomato plants, the nucleotides are assembled in a different way, but using the same 4 nucleotides as in people Problem Solving Lab 11.1 page 283 WE WILL BEGIN CONSTRUCTING A DNA MOLECULE-need 8 different colored pencils – Color code: and plain paper. – – – – – – – – Phosphate = yellow Sugar= pink Covalent Bonds=purple Hydrogen Bonds =pencil Adenine=green Thymine=red Guanine= orange Cytosine=blue Make 2 chains of P-S-P-S (20/each long) – (covalent bonds). Leave 2 inches between the 2 strands. Replication of DNA DNA in cells Where is it found? Does it leave? Why/why not? Does a cell ever need to make more DNA? Why? When? Discussion questions What if DNA was not replicated BEFORE MITOSIS? What if DNA was not replicated BEFORE MEIOSIS? Look at Figure 11.4 When a DNA molecule replicates, 2 molecules are formed. – DNA replication produces _____ molecules from one. Each molecule has one original strand, and one new strand. Please draw the first 2 steps of fig 11.4 in your notes—use 2 colors. Why are you using 2 colors?? DNA REPLICATION-THE PROCESS OF COPYING DNA Preserves the sequence of bases in an organism’s DNA There are basically 2 steps… HOW DNA IS COPIED First Step: Replication bubble forms: An enzyme breaks the hydrogen bonds between bases. Unzips a section of the double helix, exposing the bases. . Step Second : DNA polymerase (an enzyme) moves. along the 2 strands, pairing complementary bases to the exposed nucleotides one parent DNA strand This process continues until the entire DNA molecule has unzipped and been copied. WHY MUST DNA BE UNZIPPED BEFORE IT CAN BE COPIED? DNA REPLICATION Result is 2 identical DNA molecules. Semiconservative Replication-recap The 2 original strands serve as templates for 2 new strands. Follow base-pairing of Chargaff’s rule. Two complete DNA molecules result from replication. Relication preserves the sequence of bases in organism’s DNA. new old old new Problem to do: If the sequence of nitrogenous bases on one strand of a DNA molecule is : CCGAATGATTTG What would be the sequence of bases on the complimentary strand? Take out the DNA strand you began constructing earlier. Mutation-An alteration in DNA structure May 1. result from: Errors during replication – OR 2. Mutagens: an environmental agent Section 11.2 DNA to Protein DNA controls cells HOW? – Encoding instructions for making proteins – Proteins and their functions: Structural: muscles, hair Enzymes: control chemical reactions in organisms – Cellular respiration, photosynthesis, digesting food, controlling cell cycle Genes Segment of DNA that controls protein production. The specific nucleotide sequence is a “recipe” for a particular protein. What was (is) the DNA Contains instructions for molecular cause of making proteins. Lorenzo’s disease? Recall that proteins are built on __________IN THE CYTOPLASM. So how can we accomplish the protein building task? RNA is the link (let’s make a double bubble using RNA and DNA) A nucleic acid Single stranded molecule Sugar is RIBOSE Polymer – Monomers are nucleotides – C, U, A, G U=Uracil—it replaces Thymine – U base pairs with _________ 3 kinds of RNA Carry out the job of protein assembly Nucleotide Base Comparison DNA RNA Cytosine Cytosine Adenine Adenine Guanine Thymine Guanine Uracil An analogy: DNA : Project Engineer RNA’s: The workers. Production site: . ribosomes Product: proteins 3 types of RNA 1. mRNA: messenger RNA – Copies a segment of DNA, brings it to ribosome 2. rRNA: part of the ribosome – binds to rRNA, reads it. 2. tRNA: transfers amino acids to ribosome for assembly. How Proteins are made Gene Expression – Using the genetic information in DNA to make proteins. Gene Expression-2 steps 1. Transcription: Copying a portion of DNA to form an mRNA (using RNA Nucleotides) 2. Translation: 3 kinds of RNA work together to assemble amino acids into a protein molecule. ..\Bio 1\DNA\DNA animation link.mht GENE EXPRESSION Transcription Translation Transcription Practice We’ll DNA make an mRNA from ---afterward, we will learn about the UNIVERSAL GENETIC CODE” AND Then “translation” Transcription: page 290 1. enzymes unzip the DNA in the region of the gene to be transcribed. 2. Free nucleotides complimentary base pair with one strand of the DNA. THE rRNA strand breaks away & the DNA zips back up. rRNA leave nucleus, goes to cytoplasm. Plan for Today Demonstrate proficiency in translation (step 2 of protein synthesis). Do this by completing activity following instruction. 15-20 minutes of Lorenzo’s oil. Watch for effects of treatment with monounsaturated fats. The Genetic Code- Secret codes for amino acids. Nearly Universal all organisms use the same code CODON = each mRNA triplet “The Central Dogma of Biology” DNA mRNA Protein Protein Synthesis: Part 2. Translation Translating the mRNA into a sequence of amino acids to form a protein. All three RNA’s take part. ROLES OF RNA’S IN TRANSLATION mRNA has the codon tRNA carries the amino acids & translates the codon – 20 different kinds – 20 different amino acids – Has a nucleotide sequence complimentary to mRNA called an ANTICODON rRNA is part of the ribosome tRNA Each kind of tRNA carries only _____type of _________. Amino acid carried at one end. Three- base ANTICODON. This pairs up with an mRNA codon during translation. Now, theTRANSLATION STEPS 1. A ribosome attaches to an mRNA strand. 2. Amino acids brought to the ribosome by tRNA. The codon AUG codes for Methionine and signals the “start” to translation. The tRNA carrying Methionine attaches to the ribosome, translates with its Anticodon _____. 3. The ribosome slides over the mRNA to the next codon. 4. A new tRNA attached next on the mRNA, translates with its anticodon, releases its corresponding amino acid which bonds to Methionine. 4. Translation continues until a “stop” codon is reached. 5. Complete protein detaches from ribosome. 4. mRNA disassembles , so nucleotides can be reused. Translation Practice Directions: Underline the codons beginning with the start codon. Identify the corresponding anticodon and amino acid. Join the amino acids into a chain. Amino acid anticodon mRNA: G G U A U G C C U UC G G A G U U A A C A G C G UA A Translation Practice Directions: Underline the codons beginning with the start codon. Identify the corresponding anticodon and amino acid. Join the amino acids into a chain. Amino acid-------Met Proline Serine Glut Phen Threo Alanine Stop Anticodon C C A U A C G G A A G C C U C A A U U G U C G C A U U mRNA: GGUAUG CCU UCG GAG UUA ACA GCG UAA On bottom end, is an anticodon - a nucleotide sequence complimentary to mRNA. tRNA base pairs with a mRNA codon On top is the corresponding Amino Acid. . . , Section 11.3 Genetic Changes Mutations: change in ________ sequence Cuused by – – – – Errors in relpication Errors in transcription Errors in cell division External egents Mutations in reproductive cells Passed on to offspring if mutations occur in ________or __________cells Rarely have a positive effect – Important in evolution-if it permits enhanced survival capability in its environment. Mutations in body cells Not passed on to _____________> But may cause problems for the individual. Passed on in cell division. If genes controlling cell division are affected, may lead to _______. Point Mutations A change in a single ____ ____. May change the structure of a protein & its function. THE DOG BIT THE CAT THE DOG BIT THE CAR Frameshift Mutation The addition or ________ of a single base . Each codon after this would be affected—shifted. It shifts the reading codons. More harmful than point mutations. WHY??? Practice Problems Figure 11.1; answer question and prepare explanations. Problem Solving Lab 11.3 p. 299. Problem Solving Lab 11.2 p. 300. Figure 11.3 Review Structure of nucleotide Structure of DNA Where are Hydrogen bonds found in DNA molecules. All the other bonds are Covalent Bonds. GENE EXPRESSION