Chapter 12 Molecular Genetics

Transcription

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2 Section 1: DNA: The Genetic Material Section 2: Replication of DNA Section 3: DNA, RNA, and Protein Section 4: Gene Regulation and Mutation

3 12.1 DNA: The Genetic Material Objectives: 1. Summarize the experiments leading to the discovery of DNA as the genetic material. 2. Diagram and label the basic structure of DNA. 3. Describe the basic structure of the eukaryotic chromosome. Main Idea The discovery that DNA is the genetic code involved many experiments.

4 12.1 DNA: The Genetic Material Griffith Performed the first major experiment that led to the discovery of DNA as the genetic material

5 12.1 Student Notes 1. Griffith concluded that a transformation from live R bacteria to live S bacteria occurred.

6 12.1 DNA: The Genetic Material Avery Identified the molecule that transformed the R strain of bacteria into the S strain 2. Concluded that when the S cells were killed, DNA was released. R bacteria incorporated this DNA into their cells and changed into S cells.

7 12.1 DNA: The Genetic Material Hershey and Chase Used radioactive labeling to trace the DNA and protein Concluded that the viral DNA was injected into the cell and provided the genetic information needed to produce new viruses 3. Strong evidence that DNA is the transforming factor

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9 12.1 DNA: The Genetic Material DNA Structure I. Nucleotides - building blocks of nucleic acids 2. Made of a five-carbon sugar, a phosphate group, and a nitrogenous (N) base

10 3. What are the two nucleic acids? DNA, RNA 4. What are the 3 parts of a DNA nucleotide? deoxyribose, P group, N bases (A, T, C, G) 5. What is the name of the sugar in DNA? deoxyribose 6. What are the names of the 4 N bases in DNA? adenine, thymine, cytosine, guanine

11 7. Which two bases are purines? adenine and guanine 8. Which two bases are pyrimidines? thymine and cytosine 9. How do they differ in structure? purines have 2 carbon rings; pyrimidines have 1 carbon ring

12 10. What sugar does RNA have? ribose 11. What base is found only in RNA? uracil

13 12.1 DNA: The Genetic Material 12. Chargaff s rule: C = G and T = A

14 12.1 DNA: The Genetic Material X-ray Diffraction X-ray diffraction data helped solve the structure of DNA Rosalind Franklin was the female scientist who took the picture showing the helix Indicated that DNA was a double helix 13. How is the structure of DNA described? a double helix or twisted ladder 14. What women scientist took the photograph that showed this structure? Rosalind Franklin

15 The twisted ladder/double helix Video Clip Structure_and_Composition_of_DNA.asf

16 12.1 DNA: The Genetic Material Watson and Crick Built a model of the double helix that conformed to the others research 1. two outside strands consist of alternating deoxyribose and phosphate 2. cytosine and guanine bases pair to each other by three hydrogen bonds 3. thymine and adenine bases pair to each other by two hydrogen bonds

17 12.1 DNA: The Genetic Material DNA Structure DNA often is compared to a twisted ladder. Rails of the ladder are represented by the alternating deoxyribose and phosphate. The pairs of bases (cytosine guanine or thymine adenine) form the steps.

18 15. How many strands of DNA does a DNA molecule have? What scientists determined the specific structure of DNA? James Watson, Francis Crick 17. What is complimentary base pairing? The precise pairing of a purine and a pyrimidine bases (A with T; C with G).

19 12.1 DNA: The Genetic Material Orientation On the top rail, the strand is said to be oriented 5 to 3. The strand on the bottom runs in the opposite direction and is oriented 3 to 5.

20 12.1 DNA: The Genetic Material Chromosome Structure DNA coils around histones to form nucleosomes, which coil to form chromatin fibers. The chromatin fibers supercoil to form chromosomes that are visible in the metaphase stage of mitosis.

21 18. What are histones? beadlike proteins found in DNA 19. What is a nucleosome? repeating subunits of chromatin fibers consisting of DNA coiled around histones

22 Analogy

23 Word Bank chromosome, DNA, gene, human genome A is a sentence. A is a book. is the ink and paper. The is the library.

24 Word Bank chromosome, DNA, gene, human genome A gene is a sentence. A chromosome is a book. DNA is the ink and paper. The human genome is the library.

25 Arrange the following terms in order from largest to smallest. gene nucleus cell chromosome DNA

26 Arrange the following terms in order from largest to smallest. cell nucleus chromosome gene DNA

27 12.2 Replication of DNA Objectives: 1. Summarize the role of the enzymes involved in the replication of DNA. 2. Explain how leading and lagging strands are synthesized differently. Main Idea DNA replicates by making a strand that is complimentary to each original strand.

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29 12.2 DNA Replication (Honors) 1. Semiconservative Replication Parental strands of DNA separate, serve as templates, and produce DNA molecules that have one strand of parental DNA and one strand of new DNA.

30 This process occurs during interphase of mitosis and meiosis. The three main stages are: 1. Unwinding 2. Base pairing 3. Joining strands

31 12.2 Replication of DNA 2. Unwinding DNA helicase, an enzyme, unwinds and unzips the double helix. The weak H bonds are broken, leaving single strands of DNA. RNA primase adds a short segment of RNA, called an RNA primer, on each DNA strand.

32 12.2 Replication of DNA DNA polymerase continues adding appropriate nucleotides to the chain by adding to the 3 end of the new DNA strand.

33 3. Base pairing occurs when DNA polymerase catalyzes the addition of appropriate nucleotides to the new DNA strand. The nucleotides are added to the 3 end of the new DNA strand. A always binds to T and C binds to G. Two identical copies of the original doublestranded DNA are produced.

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36 12.2 Replication of DNA 4. One strand is called the leading strand and is elongated as the DNA unwinds. The other strand of DNA, called the lagging strand, elongates away from the replication fork. The lagging strand is synthesized discontinuously into small segments, called Okazaki fragments.

37 Because each strand is synthesized (made) continously and the other is made discontinuously, DNA replication is said to be semiconservative.

38 12.2 Replication of DNA 5. Joining DNA polymerase removes the RNA primer and fills in the place with DNA nucleotides. DNA ligase links the two strands together.

39 12.2 Replication of DNA Comparing DNA Replication in Eukaryotes and Prokaryotes 6. Eukaryotic DNA unwinds in multiple areas as DNA is replicated. This creates bubbles in the DNA strand. 7. In prokaryotes, DNA is circular. DNA replication occurs in two directions, just as it does in eukaryotes. DNA is located in the cytoplasm not in the nucleus as in eukaryotes.

40 8. Results of replication are that two identical copies of the original double-stranded DNA are produced. If the parent strand of DNA is ATT GCT ACC, the complimentary strand is.

41 DNA Replication

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43 Answers 1. a. thymine b. cytosine c. adenine d. guanine 2. purines 3. pyrimidines 4. DNA replication

44 5. in interphase before cell division 6. It is important for DNA to copy itself because every cell must carry the same genetic information as its parent cell. 7. DNA unzips and complimentary bases attach to each strand. Two new DNA molecules are formed.

45 8. DNA replication 1) DNA strands separate 2) base pairing occurs 3) DNA strands join by forming H bonds between the bases RESULT: 2 identical DNA molecules

46 12.3 DNA, RNA, and Protein Objectives: 1. Explain how mrna, rrna, and trna are involved in the transcription and translation of genes. 2. Summarize the role of RNA polymerase in the synthesis of mrna. 3. Describe how the code of DNA is translated into mrna and is utilized to synthesize a particular protein.

47 12.3 DNA, RNA, and Protein Main Idea /Central Dogma DNA codes for RNA, which guides protein synthesis. 1. What is the name of the process when DNA copies itself? replication 2. Where does replication occur in the cell? in the nucleus 3. What is the central dogma of biology? DNA codes for RNA, which guides protein synthesis.

48 4. What are the 2 nucleic acids? DNA and RNA

49 RNA Usually is single stranded

50 5. How does DNA differ from RNA? 1) RNA has 1 strand; DNA has 2 strands 2) the sugar ribose instead of deoxyribose 3) the base uracil instead of thymine 6. Contains the sugar ribose and the base uracil (instead of thymine)

51 12.3 DNA, RNA, and Protein Messenger RNA (mrna) Long strands of RNA nucleotides that are formed complementary to one strand of DNA Ribosomal RNA (rrna) Associates with proteins to form ribosomes in the cytoplasm Transfer RNA (trna) Smaller segments of RNA nucleotides that transport amino acids to the ribosome

52 12.3 DNA, RNA, and Protein

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54 12.3 DNA, RNA, and Protein Transcription process in which DNA makes RNA Through transcription, the DNA code is transferred to mrna in the nucleus. DNA is unzipped in the nucleus and RNA polymerase binds to a specific section where an mrna will be synthesized.

55 Transcription occurs in nucleus Amino acid CGA Amino acid UAC DNA makes mrna trna CGA GCU UAC AUG Amino acid uuu anticodon UUU AAA Ribosome codon

56 The role of transfer RNA Each trna molecule attaches to only one type of amino acid. Amino acid Chain of RNA nucleotides Transfer RNA molecule Anticodon

57 The role of transfer RNA Ribosome mrna codon

58 The role of transfer RNA A new trna molecule carrying an amino acid pairs with the second mrna codon. Alanine

59 The role of transfer RNA The amino acids are joined when a peptide bond is formed between them. Methionine Alanine Peptide bond

60 The role of transfer RNA A chain of amino acids is formed until the stop codon is reached on the mrna strand. Stop codon

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62 Translation and Protein Synthesis

63 7. What are the 3 types of RNA? mrna, rrna, trna 8. What is the name of the process in which DNA makes RNA? transcription 9. Where does transcription take place in the cell? in the nucleus 10. Which RNA carries the message from DNA in the nucleus to the cytoplasm? mrna 11.What organelle receives the mrna and is where proteins are made? ribosome

64 12.3 DNA, RNA, and Protein The Code Experiments during the 1960s demonstrated that the DNA code was a three-base code. The three-base code in DNA or mrna is called a codon.

65 12.3 DNA, RNA, and Protein RNA Processing The code on the DNA is interrupted periodically by sequences that are not in the final mrna. Intervening sequences are called introns. Remaining pieces of DNA that serve as the coding sequences are called exons. DNA and Genes

66 12.3 DNA, RNA, and Protein Translation In translation, trna molecules act as the interpreters of the mrna codon sequence. At the middle of the folded strand, there is a three-base coding sequence called the anticodon. Each anticodon is complementary to a codon on the mrna.

67 12. What is the name of the sequence of 3 bases on DNA or mrna that code for an amino acid? codon 13. Which RNA brings the amino acid to the mrna at the ribosome? trna 14. What is the name of the 3 bases located at the end of the trna molecule called? anticodon

68 15. What is at the opposite end of the trna molecule? a specific amino acid 16. What is formed when these amino acids are bonded together? a protein

69 Summary DNA contains the code to make proteins. This begins in the nucleus of a cell when DNA makes RNA in a process called transcription. mrna leaves the nucleus and takes the message to the ribosome. Here the codon of mrna joins with the anticodon of trna in a process called translation. Eventually proteins are made (synthesized).

70 12.3 DNA, RNA, and Protein Visualizing Transcription and Translation

71 The Genetic Code All organisms use the same genetic code. This provides evidence that all life on Earth evolved from a common origin.

72 12.3 DNA, RNA, and Protein One Gene One Enzyme The Beadle and Tatum experiment showed that one gene codes for one enzyme. We now know that one gene codes for one polypeptide.

73 Protein Synthesis Analogy

74 Use the following words: cytoplasm DNA (genetic code) mrna rrna trna protein ribosome

75 Automobile Factory Protein Synthesis 1. Engineers/blueprints Workers (who) Supplier (who) Factory floor (where) Assembly line (where) Car (what) 6. Cytoplasm DNA (genetic code) mrna rrna trna Protein ribosome

76 Automobile Factory Protein Synthesis 1. Engineers/blueprints 1. DNA 2. Workers 2. mrna, rrna 3. Supplier 3. trna 4. Factory floor 4. cytoplasm 5. Assembly line 5. ribosome 6. Car 6. protein

77 Mini-Lab Transcription and Translation

78 12.4 Gene Regulation and Mutation Objectives: 1. Describe how bacteria are able to regulate their genes by two types of operons. 2. Discuss how eukaryotes regulate transcription of genes. 3. Summarize the various types of mutations.

79 12.4 Gene Regulation and Mutation Prokaryote Gene Regulation Ability of an organism to control which genes are transcribed in response to the environment An operon is a section of DNA that contains the genes for the proteins needed for a specific metabolic pathway. Operator Promoter Regulatory gene Genes coding for proteins

80 12.4 Gene Regulation and Mutation The Trp Operon

81 12.4 Gene Regulation and Mutation The Lac Operon Lac-Trp Operon

82 12.4 Gene Regulation and Mutation Eukaryote Gene Regulation Controlling transcription Transcription factors ensure that a gene is used at the right time and that proteins are made in the right amounts The complex structure of eukaryotic DNA also regulates transcription.

83 12.4 Gene Regulation and Mutation Hox Genes Hox genes are responsible for the general body pattern of most animals.

84 12.4 Gene Regulation and Mutation RNA Interference RNA interference can stop the mrna from translating its message.

85 12.4 Gene Regulation and Mutation Mutations 1. A permanent change that occurs in a cell s DNA is called a mutation. Types of mutations Point mutation Insertion Deletion

86 To return to the chapter summary click escape or close this document.

87 The effects of point mutations Normal mrna Protein Stop Replace G with A Point mutation mrna Protein Stop

88 Frameshift mutations Deletion of U Frameshift mutation mrna Protein

89 To return to the chapter summary click escape or close this document.

90 2. Point mutations cause a change in just one base pair. 3. A point mutation in which one base is exchanges for another is called a substitution. 4. Missense substitutions code for the wrong amino acid. 5. Nonsense mutations change the codon for an amino acid to a stop codon.

91 6. Frameshift mutations are due to insertion or deletion and shift the amino acid sequence. 7. Certain chemicals and radiation can damage the DNA. Substances which cause mutations are called mutagens. 8. Body cell mutations are NOT passed on to the next generation. 9. Mutations in sex cells are passed on to the organism s offspring.

92 12.4 Gene Regulation and Mutation

93 12.4 Gene Regulation and Mutation Protein Folding and Stability Substitutions also can lead to genetic disorders. Can change both the folding and stability of the protein

94 12.4 Gene Regulation and Mutation Causes of Mutation Can occur spontaneously Chemicals and radiation also can damage DNA. High-energy forms of radiation, such as X rays and gamma rays, are highly mutagenic.

95 12.4 Gene Regulation and Mutation Body-cell v. Sex-cell Mutation Somatic cell mutations are not passed on to the next generation. Mutations that occur in sex cells are passed on to the organism s offspring and will be present in every cell of the offspring.

96 Chapter Resource Menu Chapter Diagnostic Questions Formative Test Questions Chapter Assessment Questions Standardized Test Practice biologygmh.com Glencoe Biology Transparencies Image Bank Vocabulary Animation Click on a hyperlink to view the corresponding lesson.

97 Chapter Diagnostic Questions 1. Which scientist(s) definitively proved that DNA transfers genetic material? A. Watson and Crick B. Mendel C. Hershey and Chase D. Avery

98 Chapter Diagnostic Questions 2. Name the small segments of the lagging DNA strand. A. ligase B. Okazaki fragments C. polymerase D. helicase

99 Chapter Diagnostic Questions 3. Which is not true of RNA? A. It contains the sugar ribose. B. It contains the base uracil. C. It is single-stranded. D. It contains a phosphate.

100 12.1 Formative Questions 1. The experiments of Avery, Hershey and Chase provided evidence that the carrier of genetic information is. A. carbohydrate B. DNA C. lipid D. protein

101 12.1 Formative Questions 2. What is the base-pairing rule for purines and pyrimidines in the DNA molecule? A. A G and C T B. A T and C G C. C A and G T D. C U and A G

102 12.1 Formative Questions 3. What are chromosomes composed of? A. chromatin and histones B. DNA and protein C. DNA and lipids D. protein and centromeres

103 12.2 Formative Questions True or False 4. The work of Watson and Crick solved the mystery of how DNA works as a genetic code.

104 12.2 Formative Questions 5. Which is not an enzyme involved in DNA replication? A. DNA ligase B. DNA polymerase C. helicase D. RNA primer

105 12.2 Formative Questions 6. During DNA replication, what nucleotide base sequence is synthesized along an original strand that has the sequence TCAAGC? A. AGTTCG B. ATGGCG C. CTGGAT D. GACCTA

106 12.3 Formative Questions 7. Which shows the basic chain of events in all organisms for reading and expressing genes? A. DNA RNA protein B. RNA DNA protein C. mrna rrna trna D. RNA processing transcription translation

107 12.3 Formative Questions 8. In the RNA molecule, uracil replaces. A. adenine B. cytosine C. purine D. thymine

108 12.3 Formative Questions 9. Which diagram shows messenger RNA (mrna)? A. C. B. D.

109 12.3 Formative Questions 10. What characteristic of the mrna molecule do scientists not yet understand?

110 12.3 Formative Questions A. intervening sequences in the mrna molecule called introns B. the original mrna made in the nucleus called the pre-mrna C. how the sequence of bases in the mrna molecule codes for amino acids D. the function of many adenine nucleotides at the 5 end called the poly-a tail

111 12.4 Formative Questions 11. Why do eukaryotic cells need a complex control system to regulate the expression of genes?

112 12.4 Formative Questions A. All of an organism s cells transcribe the same genes. B. Expression of incorrect genes can lead to mutations. C. Certain genes are expressed more frequently than others are. D. Different genes are expressed at different times in an organism s lifetime.

113 12.4 Formative Questions 12. Which type of gene causes cells to become specialized in structure in function? A. exon B. Hox gene C. intron D. operon

114 12.4 Formative Questions 13. What is an immediate result of a mutation in a gene? A. cancer B. genetic disorder C. nonfunctional enzyme D. amino acid deficiency

115 12.4 Formative Questions 14. Which is the most highly mutagenic? A. chemicals in food B. cigarette smoke C. ultraviolet radiation D. X rays

116 Chapter Assessment Questions 15. Look at the following figure. Identify the proteins that DNA first coils around.

117 Chapter Assessment Questions A. chromatin fibers B. chromosomes C. histones D. nucleosome

118 Chapter Assessment Questions 16. Explain how Hox genes affect an organism. A. They determine size. B. They determine body plan. C. They determine sex. D. They determine number of body segments.

119 Chapter Assessment Questions 17. Explain the difference between body-cell and sex-cell mutation.

120 Chapter Assessment Questions Answer: A mutagen in a body cell becomes part of the of the genetic sequence in that cell and in future daughter cells. The cell may die or simply not perform its normal function. These mutations are not passed on to the next generation. When mutations occur in sex cells, they will be present in every cell of the offspring.

121 Standardized Test Practice 1. What does this diagram show about the replication of DNA in eukaryotic cells?

122 Standardized Test Practice A. DNA is replicated only at certain places along the chromosome. B. DNA replication is both semicontinuous and conservative. C. Multiple areas of replication occur along the chromosome at the same time. D. The leading DNA strand is synthesized discontinuously.

123 Standardized Test Practice 2. What is this process called?

124 Standardized Test Practice A. mrna processing B. protein synthesis C. transcription D. translation

125 Standardized Test Practice 3. What type of mutation results in this change in the DNA sequence? TTCAGG TTCTGG A. deletion B. frameshift C. insertion D. substitution

126 Standardized Test Practice 4. How could RNA interference be used to treat diseases such as cancer and diabetes?

127 Standardized Test Practice A. by activating genes to produce proteins that can overcome the disease B. by interfering with DNA replication in cells affected by the disease C. by preventing the translation of mrna into the genes associated with the disease D. by shutting down protein synthesis in the cells of diseased tissues

128 Standardized Test Practice True or False 5. The structure of a protein can be altered dramatically by the exchange of a single amino acid for another.

129 Glencoe Biology Transparencies

130 Image Bank

131 Image Bank

132 Vocabulary Section 1 double helix nucleosome

133 Vocabulary Section 2 semiconservative replication DNA polymerase Okazaki fragment

134 Vocabulary Section 3 RNA messenger RNA ribosomal RNA transfer RNA transcription RNA polymerase codon intron exon translation

135 Vocabulary Section 4 gene regulation operon mutation mutagen

136 Animation DNA Polymerase Transcription Visualizing Transcription and Translation Lac-Trp Operon