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Chapter 12

Chapter 12. DNA & RNA. III. RNA & Protein Synthesis. The double helix structure explains how DNA is copied,but not how a gene works-_______________are coded DNA instructions that control the production of protein in the cell. A. The structure of RNA Long chain of nucleotides

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Chapter 12

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  1. Chapter 12 DNA & RNA

  2. III. RNA & Protein Synthesis • The double helix structure explains how DNA is copied,but not how a gene works-_______________are coded DNA instructions that control the production of protein in the cell. • A. The structure of RNA • Long chain of nucleotides • 3 main differences between DNA & RNA: • Sugar is ____________ • Generally single-stranded • RNA contains __________(U) in place of thymine (T) uracil ribose genes

  3. Interest Grabber Section 12-1 • Order! Order! • Genes are made of DNA, a large, complex molecule. DNA is composed of individual units called nucleotides. Three of these units form a code. The order, or sequence, of a code and the type of code determine the meaning of the message. 1. On a sheet of paper, write the word cats. List the letters or units that make up the word cats. 2. Try rearranging the units to form other words. Remember that eachnew word can have only three units. Write each word on your paper, and then add a definition for each word. 3. Did any of the codes you formed have the same meaning? 4. How do you think changing the order of the nucleotides in the DNA codon changes the codon’s message?

  4. I.DNA • A. Griffith & Transformation • Frederick Griffith was trying to figure out how bacteria made people sick-how they cause a certain type of pneumonia. • He isolated 2 strains(types) from mice-both cultured well,but only one caused pneumonia.The culture of the disease causing bacteria were __________________colonies while the other was rough. smooth

  5. 1-Griffith’s experiments (1928) • Mice injected w/ disease –causing strain got sick and died and nothing happened if injected w/other strain…He wondered if the disease-causing type made a toxin…? • So he took some of disease strain and heated to kill bacteria and then injected into mice….mice survived suggesting it was not a toxin producing disease

  6. Figure 12–2 Griffith’s Experiment Section 12-1 Heat-killed, disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Harmless bacteria (rough colonies) Control(no growth) Heat-killed, disease-causing bacteria (smooth colonies) Disease-causing bacteria (smooth colonies) Dies of pneumonia Dies of pneumonia Lives Lives Live, disease-causingbacteria (smooth colonies)

  7. Figure 12–2 Griffith’s Experiment Section 12-1 Heat-killed, disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Harmless bacteria (rough colonies) Control(no growth) Heat-killed, disease-causing bacteria (smooth colonies) Disease-causing bacteria (smooth colonies) Dies of pneumonia Dies of pneumonia Lives Lives Live, disease-causingbacteria (smooth colonies)

  8. 2-Transformation • He mixed his heat –killed w/ live harmless bacteria and injected into mice…..________________________ • Somehow the disease –causing strain passed their disease capacity to harmless bacteria….. disease –causing strain found in lungs • He called this changing of one bacteria by the genes of another _____________________....Thus a factor(gene) from heat killed disease –causing strain was passed on. Mice developed pneumonia transformation

  9. B. Avery & DNA • Team of scientists lead by Avery in 1944 repeated Griffith’s experiment in order to determine which molecule was responsible for the transformation. • They made an extract from the heat-killed bacteria and treated it w/enzymes that kill proteins,lipids and other molecules,inc. RNA

  10. Avery cont’d transformation • ____________________still occurred so the above molecules were not responsible for transformation • They repeated the experiment but used enzymes that kill____________, stopping transformation…. • Therefore ________caused the transformation and thus stores and transmits genetic info DNA DNA

  11. C. The Hershey –Chase Experiment • 1952-Alfred Hershey and Martha Chase studied viruses-disease-causing particles smaller than a cell. • ______________________-virus that infects bacteria.They have a DNA or RNA core and a protein coat…They attach to the surface of a bacterium and inject genetic info into cell.The viral genes act to produce many new bacteriophages and eventually destroy bacterial cell,w/_____________bursting out. viruses bacteriophage

  12. They grew viruses in cultures containing _________________________________,mixed them w/bacteria and waited a few min. for viruses to inject genetic material. • Then they separated the bacteria from the viruses and tested bacteria for radioactive marker…..nearly all the radioactivity was P-32-found in _________----thus concluding it was the genetic material was DNA ! Radioactive markers DNA

  13. Figure 12–4 Hershey-Chase Experiment Section 12-1 Bacteriophage with phosphorus-32 in DNA Phage infectsbacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infectsbacterium No radioactivity inside bacterium

  14. Figure 12–4 Hershey-Chase Experiment Section 12-1 Bacteriophage with phosphorus-32 in DNA Phage infectsbacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infectsbacterium No radioactivity inside bacterium

  15. Figure 12–4 Hershey-Chase Experiment Section 12-1 Bacteriophage with phosphorus-32 in DNA Phage infectsbacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infectsbacterium No radioactivity inside bacterium

  16. D. The Components and Structure of DNA • Scientists questioned how the DNA molecule could do three things 1)carry info from 1 generation to the next 2)putting that info to work and 3)could be easily copied • DNA is a long molecule made of units called ___________________________________________- nucleotides

  17. The nucleotide is made of 3 basic parts:______________________(sugar), a phosphate group and a_________________________________ deoxyribose Nitrogenous base

  18. 2 nitrogenous bases are purines(have 2 rings):___________________________(A)and_______(G) • 2 other nitrogenous bases are pyrimidines (have 1 ring):____________________(C)and ____________________________(T) Cytosine and thymine Adenine ,guanine --backbone made by sugar and phosphate w/ bases sticking out sideways

  19. Figure 12–5 DNA Nucleotides Section 12-1 Purines Pyrimidines Adenine Guanine Cytosine Thymine Phosphate group Deoxyribose

  20. 1-_______________________Rules-discovered that %’s of Cytosine and guanine were almost equal in DNA and the same was true for adenine and thymine….Thus A pairs w/T and C w/ G-BASE PAIRING Chargaff’s Rules

  21. Percentage of Bases in Four Organisms Section 12-1 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

  22. 2- X-ray evidence-1950’s –Rosalind Franklin used X-ray diffraction to learn about DNA structure----The scattered X pattern seen begins to show the __________-partial TWISTED STRUCTURE of DNA helix

  23. 3---Double helix_ • Watson and Crick -2 strands wound around each other---like the twisted ladder or spiral staircase • Strands held together by H-bonds

  24. Figure 12–7 Structure of DNA Section 12-1 Nucleotide Hydrogen bonds Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G)

  25. Interest Grabber Section 12-2 • A Perfect Copy • When a cell divides, each daughter cell receives a complete set of chromosomes. This means that each new cell has a complete set of the DNA code. Before a cell can divide, the DNA must be copied so that there are two sets ready to be distributed to the new cells.

  26. I Section 12-2 1. On a sheet of paper, draw a curving or zig-zagging line that divides the paper into two halves. Vary the bends in the line as you draw it. Without tracing, copy the line on a second sheet of paper. 2. Hold the papers side by side, and compare the lines. Do they look the same? 3. Now, stack the papers, one on top of the other, and hold the papers up to the light. Are the lines the same? 4. How could you use the original paper to draw exact copies of the line without tracing it? 5. Why is it important that the copies of DNA that are given to new daughter cells be exact copies of the original?

  27. II. Chromosomes & DNA Replication • A-DNA & Chromosomes • In cytoplasm in prokaryotes • In _______________________found in cell nucleus in the form of a number of chromosomes(46 humans,8 Drosophilia and 22 Sequoia trees) eukaryotes

  28. 1--DNA length • 1.6 mm in E.coli(has 4,639,221 base pairs)---obviously it must be tightly folded

  29. 2-Chromosome Structure • Eukaryotic cells have about 1000 times as many base pairs of DNA than a bacterium • Humans cells have ~ 1 m DNA • Eukaryotic chromosomes contain DNA and a protein ,which together make _____________________-consisting of DNA tightly packed around proteins called histones chromatin

  30. DNA and histone together make beadlike_____________________________ • Nucleosomes pack together to make thick fibers,drawn together during mitosis…also separating • Role of nucleosomes-fold great lengths of DNA into tiny spaces nucleosomes

  31. Prokaryotic Chromosome Structure Section 12-2 Chromosome E.coli bacterium Bases on the chromosome

  32. Figure 12-10 Chromosome Structure of Eukaryotes Section 12-2 Nucleosome Chromosome DNA double helix Coils Supercoils Histones

  33. B. DNA Replication • Each strand of DNA double helix has all the info to___________________________by base pairing • Strands are complementary • In prokaryotes,this begins @single point and proceeds-often in 2 directions • In Eukaryotes,DNA replication begins @ 100’s of places,going both directions until complete • __________________________is where replication occurs Reconstruct the other half Replication fork

  34. 1-Duplicating DNA • __________________________or duplication of DNA happens before cell division---ensuring each cell has a complete set of DNA molecules • Each strand of a double helix serves as a _____________________or model for new strand • A pairs w/ T and C w/ G template replication

  35. 2-How Replication Occurs • Carried out by a series of enzymes that unzip a molecule • ____________________________________ joins individual nucleotides to make a DNA molecule….also proof reads the new strands DNA polymerase

  36. Figure 12–11 DNA Replication Section 12-2 Original strand DNA polymerase New strand Growth DNA polymerase Growth Replication fork Replication fork Nitrogenous bases New strand Original strand

  37. III. RNA & Protein Synthesis • The double helix structure explains how DNA is copied,but not how a gene works-_______________are coded DNA instructions that control the production of protein in the cell. • A) The structure of RNA • Long chain of nucleotides • 3 main differences between DNA & RNA: • 1--Sugar is _________________ • 2---Generally single-stranded • 3---RNA contains ________________(U) in place of thymine (T) ribose uracil genes

  38. Protein synthesis B. Types of RNA • Main job=_________________-ie the assembly of amino acids into proteins • 3 Types: • ____________________(mRNA)-carry copies for instructions from DNA to rest of cell • ____________________(rRNA)-type of RNA that helps make up ribosomes,where proteins assembled • ________________(tRNA)transfers each amino acid to the ribosome as it is coded for on mRNA. messenger ribosomal Transfer

  39. Messenger RNA Ribosomal RNA Transfer RNA Bringamino acids toribosome Combine with proteins tRNA mRNA Carry instructions rRNA DNA Ribosome Ribosomes Concept Map Section 12-3 RNA can be which functions to also called also called which functions to also called which functions to from to to make up

  40. C. Transcription-produces RNA molecules by copying part of nucleotide sequence of DNA into a complementary sequence in RNA • Requires enzyme known as _______________________________________-binds to DNA and separates DNA strands.Then uses one strand as template to make RNA • The enzyme only binds to areas known as promoters-signals that indicate where to make RNA.Similar signals tell where to stop RNA-polymerase

  41. Figure 12–14 Transcription Section 12-3 Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) RNApolymerase DNA RNA

  42. D. RNA editing • ________________________ in eukaryotic genes ,sequences of nucleotides that ARE NOT involved in coding for proteins • _______________________-DNA sequence that does code for protein exons introns

  43. E. Genetic Code polypeptide • ______________________-chain of amino acids=proteins • _________________-3 consecutive nucleotides that specify a specific amino acid • Example –UCGCACGGU reads UCG_CAC_GGU and codes for Serine-Histidine-Glycine codon

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