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Click on a lesson name to select. Chapter 12 Molecular Genetics Section 1: DNA: The Genetic Material Section 2: Replication of DNA Section 3: DNA, RNA,

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Presentation on theme: "Click on a lesson name to select. Chapter 12 Molecular Genetics Section 1: DNA: The Genetic Material Section 2: Replication of DNA Section 3: DNA, RNA,"— Presentation transcript:

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3 Click on a lesson name to select. Chapter 12 Molecular Genetics Section 1: DNA: The Genetic Material Section 2: Replication of DNA Section 3: DNA, RNA, and Protein Section 4: Gene Regulation and Mutation

4 12.1 DNA: The Genetic Material Molecular Genetics Chapter 12 Griffith Performed the first major experiment that led to the discovery of DNA as the genetic material

5 DNA is the genetic material –The First demonstration of bacterial transformation. –Experiments done by Frederick Griffith (in London) in 1928 found there were two different types of the bacterium Streptococcus pneumoniae: An "S" or SMOOTH coat strain, which is lethal to mice. An "R" or ROUGH strain, which will not hurt the mouse. –Griffith found that he could heat inactivate the smooth strain.

6 Fredrick Griffith However, if he were to take a mixture of the heat-inactivated S strain, mixed with the R strain, the mouse would die. Thus there was some material in the heat-killed S strain that was responsible for "transforming" the R strain into a lethal form. Fred Griffith (and a lab co-worker) was killed in their laboratory in 1940 from a German bomb.

7 Griffiths work continued in U.S. in 1944, Oswald Avery, C.M. MacLeod, and M. McCarty carefully demonstrated that the ONLY material that was responsible for the transformation was DNA Thus, DNA was the "Genetic material" - however, many scientists were still not sure that it was REALLY DNA (and not proteins) that was the genetic material.

8 Molecular Genetics Oswald Avery Identified the molecule that transformed the R strain of bacteria into the S strain Concluded that when the S cells were killed, DNA was released R bacteria incorporated this DNA into their cells and changed into S cells DNA: The Genetic Material Chapter 12

9 Molecular Genetics Hershey and Chase (1952) Used radioactive labeling to trace the DNA (P) and protein (S) Concluded that the viral DNA was injected into the cell and provided the genetic information needed to produce new viruses 12.1 DNA: The Genetic Material Chapter 12

10 Molecular Genetics Chapter 12

11 Molecular Genetics DNA Structure Nucleotides Consist of a five-carbon sugar, a phosphate group, and a nitrogenous base 12.1 DNA: The Genetic Material Chapter 12

12 Molecular Genetics Chargaffs rule: C = G and T = A Pyrimidines = Cytosine and Thymine Purines = Guanine and Adenine 12.1 DNA: The Genetic Material Chapter 12 In 1950, Erwin Chargaff analyzed the base composition of DNA composition in a number of organisms. He reported that DNA composition varies from one species to another. Such evidence of molecular diversity, which had been presumed absent from DNA, made DNA a more credible candidate for the genetic material than protein.

13 Molecular Genetics X-ray Diffraction Structure Analysis ( ) X-ray diffraction data helped solve the structure of DNA Indicated that DNA was a double helix 12.1 DNA: The Genetic Material Chapter 12 This is the famous Rosalind Franklin - Picture 51 which was leaked to James Watson and Francis Crick by Maurice Wilkins. Sodium deoxyribose nucleate from calf thymus, Structure B, Photo 51, taken by Rosalind E. Franklin and R.G. Gosling (her student). Linus Pauling's holographic annotations are to the right of the photo. May 2, 1952

14 Molecular Genetics X-ray Diffraction Rosalind Franklin ( ) 12.1 DNA: The Genetic Material Chapter 12 The technique with which Maurice Wilkins and Franklin set out to do this is called X-ray crystallography. With this technique a crystal is exposed to x-rays in order to produce a diffraction pattern. If the crystal is pure enough and the diffraction pattern is acquired very carefully, it is possible to reconstruct the positions of the atoms in the molecules that comprise the basic unit of the crystal. Rosalind Franklin died from cancer in April of 1958, at the age of 37.

15 Molecular Genetics Watson and Crick 1953 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 12.1 DNA: The Genetic Material Chapter 12

16 Nobel Prize in Medicine/Physiology The rules of the Nobel Prize forbid posthumous nominations; because Rosalind Franklin had died in 1958 she was not eligible for nomination to the Nobel Prize subsequently awarded to Crick, Watson, and Wilkins in The award was for their body of work on nucleic acids and not exclusively for the discovery of the structure of DNA.nucleic acids By the time of the award Wilkins had been working on the structure of DNA for over 10 years, and had done much to confirm the Crick-Watson model. Crick had been working on the genetic code at Cambridge and Watson had worked on RNA for some years.genetic codeRNA

17 Molecular Genetics DNA Structure – Double Helix 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 DNA: The Genetic Material Chapter 12

18 Molecular Genetics 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 DNA: The Genetic Material Chapter 12

19 12.1 DNA: The Genetic Material Molecular Genetics 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. Chapter 12

20 12.2 Replication of DNA Molecular Genetics 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. Chapter 12

21 Molecular Genetics Unwinding DNA helicase, an enzyme, is responsible for unwinding and unzipping the double helix. RNA primase adds a short segment of RNA, called an RNA primer, on each DNA strand. Keeping the DNA strands separate Replication of DNA Chapter 12

22 Molecular Genetics Base pairing DNA polymerase (an enzyme) continues adding appropriate nucleotides to the chain by adding to the 3 end of the new DNA strand Replication of DNA Chapter 12

23 Molecular Genetics Chapter 12

24 Molecular Genetics One strand is called the leading strand and is elongated as the DNA unwinds so is said to be synthesized continuously. 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 Replication of DNA Chapter 12

25 Molecular Genetics Joining DNA polymerase removes the RNA primer and fills in the place with DNA nucleotides. DNA ligase links the two sections Replication of DNA Chapter 12

26 12.2 Replication of DNA Molecular Genetics Comparing DNA Replication in Eukaryotes and Prokaryotes Eukaryotic DNA unwinds in multiple areas as DNA is replicated. In prokaryotes, the circular DNA strand is opened at one origin of replication. Chapter 12

27 12.3 DNA, RNA, and Protein Molecular Genetics Central Dogma: DNA to RNA to Protein RNA Contains the sugar ribose (instead of deoxyribose) and the base uracil (instead of thymine) Usually is single stranded Chapter 12

28 Molecular Genetics 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 where proteins are made by adding 1 a.a. at a time 12.3 DNA, RNA, and Protein Chapter 12

29 Molecular Genetics 12.3 DNA, RNA, and Protein Chapter 12

30 Molecular Genetics Chapter 12

31 DNA is unzipped in the nucleus and RNA polymerase binds to a specific section where an mRNA will be synthesized. Molecular Genetics Transcription Through transcription, the DNA code is transferred to mRNA in the nucleus DNA, RNA, and Protein Chapter 12

32 Molecular Genetics Chapter 12

33 Molecular Genetics RNA Processing The code on the DNA is interrupted periodically by sequences that are not in the final mRNA – introns removed.. Intervening sequences are called introns. Remaining pieces of DNA that serve as the coding sequences are called exons DNA, RNA, and Protein Chapter 12 DNA and Genes

34 Molecular Genetics 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 DNA, RNA, and Protein Chapter 12

35 Molecular Genetics 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 DNA, RNA, and Protein Chapter 12

36 Molecular Genetics 12.3 DNA, RNA, and Protein Chapter 12 Visualizing Transcription and Translation

37 12.3 DNA, RNA, and Protein Molecular Genetics 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. Chapter 12 DNA from the Beginning

38 12.4 Gene Regulation and Mutation Molecular Genetics 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 Chapter 12

39 Molecular Genetics The Trp Operon 12.4 Gene Regulation and Mutation Chapter 12

40 Molecular Genetics The Lac Operon 12.4 Gene Regulation and Mutation Chapter 12 Lac-Trp Operon

41 Molecular Genetics 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 Gene Regulation and Mutation Chapter 12

42 Molecular Genetics Hox Genes Hox genes are responsible for the general body pattern of most animals Gene Regulation and Mutation Chapter 12

43 Molecular Genetics RNA Interference RNA interference can stop the mRNA from translating its message Gene Regulation and Mutation Chapter 12

44 Molecular Genetics Mutations A permanent change that occurs in a cells DNA is called a mutation. Types of mutations Point mutation Insertion Deletion 12.4 Gene Regulation and Mutation Chapter 12

45 Molecular Genetics 12.4 Gene Regulation and Mutation Chapter 12

46 Molecular Genetics Protein Folding and Stability Substitutions also can lead to genetic disorders. Can change both the folding and stability of the protein 12.4 Gene Regulation and Mutation Chapter 12

47 Molecular Genetics 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 Gene Regulation and Mutation Chapter 12

48 Molecular Genetics 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 organisms offspring and will be present in every cell of the offspring Gene Regulation and Mutation Chapter 12

49 Molecular Genetics 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. Chapter 12

50 A. Watson and Crick B. Mendel C. Hershey and Chase D. Avery Which scientist(s) definitively proved that DNA transfers genetic material? Molecular Genetics Chapter Diagnostic Questions Chapter 12

51 A. ligase B. Okazaki fragments C. polymerase D. helicase Name the small segments of the lagging DNA strand. Molecular Genetics Chapter Diagnostic Questions Chapter 12

52 A. It contains the sugar deoxyribose. B. It contains the base uracil. C. It is single-stranded. D. It contains a phosphate. Which is not true of RNA? Molecular Genetics Chapter Diagnostic Questions Chapter 12

53 A. carbohydrate B. DNA C. lipid D. protein The experiments of Avery, Hershey and Chase provided evidence that the carrier of genetic information is _______. Molecular Genetics 12.1 Formative Questions Chapter 12

54 A. AG and CT B. AT and CG C. CA and GT D. CU and AG What is the base-pairing rule for purines and pyrimidines in the DNA molecule? Molecular Genetics 12.1 Formative Questions Chapter 12

55 A.chromatin and histones B. DNA and protein C. DNA and lipids D. protein and centromeres What are chromosomes composed of? Molecular Genetics 12.1 Formative Questions Chapter 12

56 True or False The work of Watson and Crick solved the mystery of how DNA works as a genetic code. Molecular Genetics 12.2 Formative Questions Chapter 12

57 A. DNA ligase B. DNA polymerase C. Helicase D. RNA primer Which is not an enzyme involved in DNA replication? Molecular Genetics 12.2 Formative Questions Chapter 12

58 A. AGTTCG B. ATGGCG C. CTGGAT D. GACCTA During DNA replication, what nucleotide base sequence is synthesized along an original strand that has the sequence TCAAGC? Molecular Genetics 12.2 Formative Questions Chapter 12

59 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 Molecular Genetics D. RNA processing transcription translation 12.3 Formative Questions Chapter 12

60 In the RNA molecule, uracil replaces _______. A. adenine B. cytosine C. purine D. thymine Molecular Genetics 12.3 Formative Questions Chapter 12

61 Which diagram shows messenger RNA (mRNA)? Molecular Genetics 12.3 Formative Questions Chapter 12 A. B. C. D.

62 What characteristic of the mRNA molecule do scientists not yet understand? Molecular Genetics 12.3 Formative Questions Chapter 12

63 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 Molecular Genetics 12.3 Formative Questions Chapter 12

64 Why do eukaryotic cells need a complex control system to regulate the expression of genes? Molecular Genetics 12.4 Formative Questions Chapter 12

65 A. All of an organisms 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 organisms lifetime. Molecular Genetics 12.4 Formative Questions Chapter 12

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

67 What is an immediate result of a mutation in a gene? A. cancer B. genetic disorder C. nonfunctional enzyme D. amino acid deficiency Molecular Genetics 12.4 Formative Questions Chapter 12

68 Which is the most highly mutagenic? A. chemicals in food B. cigarette smoke C. ultraviolet radiation D. X rays Molecular Genetics 12.4 Formative Questions Chapter 12

69 Look at the following figure. Identify the proteins that DNA first coils around. Molecular Genetics Chapter Assessment Questions Chapter 12

70 A. chromatin fibers B. chromosomes C. histones D. nucleosome Molecular Genetics Chapter Assessment Questions Chapter 12

71 A. They determine size. B. They determine body plan. C. They determine sex. Explain how Hox genes affect an organism. Molecular Genetics Chapter Assessment Questions Chapter 12 D. They determine number of body segments.

72 Explain the difference between body-cell and sex-cell mutation. Molecular Genetics Chapter Assessment Questions Chapter 12

73 Molecular Genetics Answer: A mutagen in a body cell becomes part 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. Chapter Assessment Questions Chapter 12

74 What does this diagram show about the replication of DNA in eukaryotic cells? Molecular Genetics Standardized Test Practice Chapter 12

75 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. Molecular Genetics Standardized Test Practice Chapter 12

76 What is this process called? Molecular Genetics Standardized Test Practice Chapter 12

77 A. mRNA processing B. protein synthesis C. transcription D. translation Molecular Genetics Standardized Test Practice Chapter 12

78 What type of mutation results in this change in the DNA sequence? A. deletion B. frameshift C. insertion D. substitution TTCAGG TTCTGG Molecular Genetics Standardized Test Practice Chapter 12

79 How could RNA interference be used to treat diseases such as cancer and diabetes? Molecular Genetics Standardized Test Practice Chapter 12

80 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 Molecular Genetics Standardized Test Practice Chapter 12

81 True or False The structure of a protein can be altered dramatically by the exchange of a single amino acid for another. Molecular Genetics Standardized Test Practice Chapter 12

82 Molecular Genetics Glencoe Biology Transparencies Chapter 12

83 Molecular Genetics Image Bank Chapter 12

84 Molecular Genetics Image Bank Chapter 12

85 double helix nucleosome Molecular Genetics Vocabulary Section 1 Chapter 12

86 semiconservative replication DNA polymerase Okazaki fragment Molecular Genetics Vocabulary Section 2 Chapter 12

87 RNA messenger RNA ribosomal RNA transfer RNA transcription RNA polymerase codon intron exon translation Molecular Genetics Vocabulary Section 3 Chapter 12

88 gene regulation operon mutation mutagen Molecular Genetics Vocabulary Section 4 Chapter 12

89 Molecular Genetics DNA Polymerase Transcription Visualizing Transcription and Translation Visualizing Transcription and Translation Lac-Trp Operon Animation Chapter 12


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