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Order! Order!

Order! Order!

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Order! Order!

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  1. 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 each new 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?

  2. Section Outline Section 12-1 • 12–1 DNA A. Griffith and Transformation 1. Griffith’s Experiments 2. Transformation B. Avery and DNA C. The Hershey-Chase Experiment 1. Bacteriophages 2. Radioactive Markers D. The Components and Structure of DNA 1. Chargaff’s Rules 2. X-Ray Evidence 3. The Double Helix

  3. Section 12-1 • 1928-British scientist, F. Griffith, was studying two strains of bacteria that were associated with pneumonia • -one strain caused pneumonia (smooth) • -other strain was harmless (rough) • Initial experiment • a. inject mice with smooth strain-death • b. inject mice with rough strain-live • c. Inject mice with heat-killed smooth strain-live

  4. Section 12-1 • Second experiment • mixed heat-killed, disease-causing bacteria with the live harmless bacteria-death • - when he pulled fluids from the dead mice’s lungs he found living smooth bacteria. • Griffith’s hypothesis: • transformation-process in which one strain of bacteria is changed by a gene or genes from another strain of bacteria

  5. 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)

  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. Video 1 Video 1

  8. Section 12-1 • 1944-O. Avery repeated Griffith’s work to determine which molecule in the heat-killed bacteria was most important for transformation • Initial experiment-destroyed the proteins, lipids, carbohydrates, and RNA of the heat-killed bacteria with enzymes-transformation still takes place when added to harmless bacteria • Second experiment-used enzymes to break down the molecule DNA and then added to this to the harmless bacteria-no transformation • Conclusion: DNA stores and transmits genetic information from generation to generation.

  9. Section 12-1 • 1952-Hershey and Chase designed an experiment to verify that genes were made of DNA using bacteriophages (viruses that attaches to bacteria, injects its DNA into the bacteria, and causes the bacteria to produce more viruses) • Grew virus cultures in radioactive isotopes that would mark either the protein coat or DNA. • Hershey and Chase concluded that the genetic material of the bacteriophage was DNA

  10. 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

  11. 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

  12. 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

  13. Section 12-1 • Components and Structure of DNA • 1. Long molecule made of units called nucleotides • 2. Nucleotides composed of: • a. Deoxyribose-5-carbon sugar • b. Phosphate group • c. Nitrogenous base

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

  15. Section 12-1 • Chargaff’s Rules • States that the percentage of guanine and cytosine present in DNA are equal and that adenine and thymine are also equal. • A=T • C=G

  16. 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

  17. Section 12-1 • 1950’s-X-ray evidence gathered by Franklin was used by Watson and Crick to further develop the double helix model of DNA in which two strands were wound around each other.

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

  19. 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.

  20. 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?

  21. Section Outline Section 12-2 • 12–2 Chromosomes and DNA Replication A. DNA and Chromosomes 1. DNA Length 2. Chromosome Structure B. DNA Replication 1. Duplicating DNA 2. How Replication Occurs

  22. Section 12-2 • PROKARYOTES • Prokaryotic cells lack nuclei and membrane-bound organelles. Their DNA is located in the cytoplasm usually as a single circular DNA molecule that contains nearly all of the cell’s genetic information. This is the prokaryotic cell’s chromosome.

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

  24. Section 12-2 • EUKARYOTES • Eukaryotic cells can have up to 1000 times more DNA • DNA is generally found in nucleus in the form of a number of chromosomes • ex. Diploid human cells=46 chromosomes

  25. Section 12-2 • DNA Length • The relative length of DNA is very long. The chromosome of bacteria, E. coli, is 1.6 mm. This is 1000 times longer than the bacteria itself. • Chromosome Structure • The DNA in a Eukaryotic cell is packed even tighter. The nucleus of a human cell contains more than a meter of DNA!

  26. Nucleosome Chromosome DNA double helix Coils Supercoils Histones Figure 12-10 Chromosome Structure of Eukaryotes Section 12-2 DNA is tightly coiled around a protein called histones to form a substance called chromatin. Each histone molecule along with the DNA that is coiled around it is called a nucleosome. Nucleosomes enable cells to fold enormous lengths of DNA into the cell’s nucleus.

  27. Section 12-2 • DNA Replication • Before a cell divides it duplicates its DNA in a copying process called replication. The DNA molecule separates into two strands, and then forms two new complementary strands following the base pair rules • Replication forks are the separation of the two strands of DNA that allow replication. These forks are created by an enzyme that “unzips” the DNA molecule. Another enzyme called DNA polymerase joins individual nucleotides to the two strands producing two identical DNA molecules.

  28. 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

  29. Video 2 Video 2

  30. Section 12-3 • Information, Please • DNA contains the information that a cell needs to carry out all of its functions. In a way, DNA is like the cell’s encyclopedia. Suppose that you go to the library to do research for a science project. You find the information in an encyclopedia. You go to the desk to sign out the book, but the librarian informs you that this book is for reference only and may not be taken out. 1. Why do you think the library holds some books for reference only? 2. If you can’t borrow a book, how can you take home the information in it? 3. All of the parts of a cell are controlled by the information in DNA, yet DNA does not leave the nucleus. How do you think the information in DNA might get from the nucleus to the rest of the cell?

  31. Section Outline Section 12-3 • 12–3 RNA and Protein Synthesis A. The Structure of RNA B. Types of RNA C. Transcription D. RNA Editing E. The Genetic Code F. Translation G. The Roles of RNA and DNA H. Genes and Proteins

  32. Section 12-3 • RNA and Protein Synthesis • Genes-sequence of DNA that codes for production of a protein thus determines a trait • This segment of DNA is copied into RNA and transferred outside of the nucleus to the site of protein synthesis. • Structure of RNA • RNA consists of a long chain of nucleotides, similar to DNA; however there are 3 main differences: • 1. Ribose instead of Deoxyribose • 2. RNA is generally single stranded • 3. Uracil instead of Thymine

  33. Section 12-3 • Types of RNA • The main function of RNA is to control the assembly of amino acids into proteins- protein synthesis • 3 Types of RNA: • 1. messenger RNA(mRNA)-carries instructions from the DNA to the rest of the cell • 2. ribosomal RNA(rRNA)-helps make up ribosomes along with several proteins • 3. transfer RNA(tRNA)- transfers each amino acid to the ribosome as coded by mRNA

  34. Section 12-3 • Transcription • This is when an RNA molecule is produced by copying part of the DNA strand into a complementary sequence of RNA. It is accomplished by an enzyme (RNA polymerase) binding to and separating the DNA strands. RNA polymerase then uses one strand of DNA as template to assemble the sequence of RNA. • promoters-site on DNA in which the enzymes will bind

  35. 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

  36. Video 3 Video 3

  37. Section 12-3 • RNA Editing- • RNA molecules require editing before they leave the nucleus and are used to assemble proteins. • introns-sequences of nucleotides not involved in coding for proteins • exons-sequences that are expressed in protein synthesis

  38. Section 12-3 • The Genetic Code • Proteins are made up of long chains of amino acids called polypeptides. The order in which these amino acids are assembled is determined by the order of the nucleotides on the strand of mRNA. During translation , the code is read three nucleotides at a time. This is known as a codon. • Example UCGCACGGU UCG-CAC-GGU • serine-histidine-glycine

  39. Figure 12–17 The Genetic Code Section 12-3

  40. Section 12-3 • Translation • The decoding of an mRNA molecule into a polypeptide chain and ultimately a protein.

  41. Figure 12–18 Translation Section 12-3

  42. Figure 12–18 Translation (continued) Section 12-3

  43. Video 4 Video 4

  44. 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 also called which functions to also called which functions to also called which functions to from to to make up

  45. Section 12-4 • Determining the Sequence of a Gene • DNA contains the code of instructions for cells. Sometimes, an error occurs when the code is copied. Such errors are called mutations.

  46. Section 12-4 1. Copy the following information about Protein X: Methionine—Phenylalanine—Tryptophan—Asparagine—Isoleucine—STOP. 2. Use Figure 12–17 on page 303 in your textbook to determine one possible sequence of RNA to code for this information. Write this code below the description of Protein X. Below this, write the DNA code that would produce this RNA sequence. 3. Now, cause a mutation in the gene sequence that you just determined by deleting the fourth base in the DNA sequence. Write this new sequence. 4. Write the new RNA sequence that would be produced. Below that, write the amino acid sequence that would result from this mutation in your gene. Call this Protein Y. 5. Did this single deletion cause much change in your protein? Explain your answer.

  47. Figure 12–17 The Genetic Code Section 12-3

  48. Section Outline Section 12-4 • 12–4 Mutations A. Kinds of Mutations 1. Gene Mutations 2. Chromosomal Mutations B. Significance of Mutations

  49. Section 12-4 • Mutations are changes in the genetic material. • Point mutations -gene mutations involving changes in one or a few nucleotides. These include: • a. Substitutions

  50. Section 12-4 • Frameshift mutations -gene mutations in which one nucleotide change can alter the assembly of every amino acid that follows the point of the mutation. • a. Insertions • b. Deletions