1. © 2010 Pearson Education, Inc. Lectures by Chris C. Romero, updated by Edward J. Zalisko PowerPoint ® Lectures for Campbell Essential Biology, Fourth Edition – Eric Simon, Jane Reece, and Jean Dickey Campbell Essential Biology with Physiology, Third Edition – Eric Simon, Jane Reece, and Jean Dickey Chapter 11 How Genes Are Controlled

2. Biology and Society: Tobacco’s Smoking Gun During the 1900s, doctors noticed that –Smoking increased –Lung cancer increased © 2010 Pearson Education, Inc.

3. Figure 11.00

4. © 2010 Pearson Education, Inc. In 1996, researchers studying lung cancer found that, in human lung cells growing in the lab, a component of tobacco smoke, BPDE, binds to DNA within a gene called p53, which codes for a protein that normally helps suppress the formation of tumors. This work directly linked a chemical in tobacco smoke with the formation of human lung tumors.

5. © 2010 Pearson Education, Inc. HOW AND WHY GENES ARE REGULATED Every somatic cell in an organism contains identical genetic instructions. –They all share the same genome. –So what makes them different?

6. © 2010 Pearson Education, Inc. In cellular differentiation, cells become specialized in –Structure –Function Certain genes are turned on and off in the process of gene regulation.

7. © 2010 Pearson Education, Inc. Patterns of Gene Expression in Differentiated Cells In gene expression –A gene is turned on and transcribed into RNA –Information flows from –Genes to proteins –Genotype to phenotype Information flows from DNA to RNA to proteins.

8. © 2010 Pearson Education, Inc. The great differences among cells in an organism must result from the selective expression of genes.

9. Gene for a glycolysis enzyme Hemoglobin gene Antibody gene Insulin gene White blood cell Pancreas cell Nerve cell Active gene Key Colorized TEM Colorized SEM Figure 11.1

10. © 2010 Pearson Education, Inc. Gene Regulation in Bacteria Natural selection has favored bacteria that express –Only certain genes –Only at specific times when the products are needed by the cell So how do bacteria selectively turn their genes on and off?

11. © 2010 Pearson Education, Inc. An operon includes –A cluster of genes with related functions –The control sequences that turn the genes on or off The bacterium E. coli used the lac operon to coordinate the expression of genes that produce enzymes used to break down lactose in the bacterium’s environment.

12. © 2010 Pearson Education, Inc. The lac operon uses –A promoter, a control sequence where the transcription enzyme initiates transcription –An operator, a DNA segment that acts as a switch that is turned on or off –A repressor, which binds to the operator and physically blocks the attachment of RNA polymerase

13. Operon turned on (lactose inactivates repressor) Lactose Protein mRNA Lactose enzymes DNA Protein mRNA DNA Operon turned off (lactose absent) Translation Inactive repressor RNA polymerase bound to promoter Transcription Active repressor RNA polymerase cannot attach to promoter Regulatory gene Promoter Operator Operon Genes for lactose enzymes Figure 11.2

14. Protein mRNA DNA Operon turned off (lactose absent) Active repressor RNA polymerase cannot attach to promoter Regulatory gene Promoter Operator Operon Genes for lactose enzymes Figure 11.2a

15. Operon turned on (lactose inactivates repressor) Lactose Protein mRNA Lactose enzymes DNA Translation Inactive repressor RNA polymerase bound to promoter Transcription Figure 11.2b

16. © 2010 Pearson Education, Inc. Gene Regulation in Eukaryotic Cells Eukaryotic cells have more complex gene regulating mechanisms with many points where the process can be regulated, as illustrated by this analogy to a water supply system with many control valves along the way.

17. DNA Unpacking of DNA Chromosome Gene Figure 11.3-1

18. DNA Transcription of gene Unpacking of DNA Chromosome Gene RNA transcript IntronExon Figure 11.3-2

19. DNA Flow of mRNA through nuclear envelope Processing of RNA Transcription of gene Unpacking of DNA Chromosome Gene RNA transcript IntronExon mRNA in nucleus Tail Cap mRNA in cytoplasm Nucleus Cytoplasm Figure 11.3-3

20. DNA Flow of mRNA through nuclear envelope Processing of RNA Transcription of gene Unpacking of DNA Chromosome Gene RNA transcript IntronExon mRNA in nucleus Tail Cap mRNA in cytoplasm Nucleus Cytoplasm Breakdown of mRNA Figure 11.3-4

21. DNA Flow of mRNA through nuclear envelope Processing of RNA Transcription of gene Unpacking of DNA Chromosome Gene RNA transcript IntronExon mRNA in nucleus Tail Cap mRNA in cytoplasm Nucleus Cytoplasm Breakdown of mRNA Translation of mRNA Polypeptide Figure 11.3-5

22. DNA Flow of mRNA through nuclear envelope Processing of RNA Transcription of gene Unpacking of DNA Chromosome Gene RNA transcript IntronExon mRNA in nucleus Tail Cap mRNA in cytoplasm Nucleus Cytoplasm Breakdown of mRNA Translation of mRNA Various changes to polypeptide Active protein Polypeptide Figure 11.3-6

23. DNA Flow of mRNA through nuclear envelope Processing of RNA Transcription of gene Unpacking of DNA Chromosome Gene RNA transcript IntronExon mRNA in nucleus Tail Cap mRNA in cytoplasm Nucleus Cytoplasm Breakdown of mRNA Translation of mRNA Breakdown of protein Various changes to polypeptide Active protein Polypeptide Figure 11.3-7

24. © 2010 Pearson Education, Inc. The Regulation of DNA Packing Cells may use DNA packing for long-term inactivation of genes.

25. © 2010 Pearson Education, Inc. X chromosome inactivation –Occurs in female mammals –Is when one of the two X chromosomes in each cell is inactivated at random All of the descendants will have the same X chromosome turned off.

26. © 2010 Pearson Education, Inc. If a female cat is heterozygous for a gene on the X chromosome –About half her cells will express one allele –The others will express the alternate allele

27. Cell division and X chromosome inactivation Allele for orange fur Early embryo: X chromosomes Allele for black fur Inactive X Active X Inactive X Active X Orange fur Two cell populations in adult cat: Black fur Figure 11.4

28. Cell division and X chromosome inactivation Allele for orange fur Early embryo: X chromosomes Allele for black fur Inactive X Active X Inactive X Active X Orange fur Two cell populations in adult cat: Black fur Figure 11.4a

29. © 2010 Pearson Education, Inc. The Initiation of Transcription The initiation of transcription is the most important stage for regulating gene expression. In prokaryotes and eukaryotes, regulatory proteins –Bind to DNA –Turn the transcription of genes on and off

30. © 2010 Pearson Education, Inc. Unlike prokaryotic genes, transcription in eukaryotes is complex, involving many proteins, called transcription factors, that bind to DNA sequences called enhancers. Animation: Initiation of Transcription

31. Bend in the DNA Enhancers (DNA control sequences) Transcription factor Transcription Promoter Gene RNA polymerase Figure 11.5

32. © 2010 Pearson Education, Inc. Repressor proteins called silencers –Bind to DNA –Inhibit the start of transcription Activators are –More typically used by eukaryotes –Turn genes on by binding to DNA

33. © 2010 Pearson Education, Inc. RNA Processing and Breakdown The eukaryotic cell –Localizes transcription in the nucleus –Processes RNA in the nucleus

34. © 2010 Pearson Education, Inc. RNA processing includes the –Addition of a cap and tail to the RNA –Removal of any introns –Splicing together of the remaining exons

35. © 2010 Pearson Education, Inc. In alternative RNA splicing, exons may be spliced together in different combinations, producing more than one type of polypeptide from a single gene. Animation: RNA Processing Animation: mRNA Degradation Animation: Blocking Translation

36. Exons DNA 1 2 3 5 4 Figure 11.6-1

37. RNA transcript Exons DNA 1 2 3 4 1 2 3 5 5 4 Figure 11.6-2

38. RNA transcript Exons RNA splicing mRNA DNA or 1 2 3 5 1 2 4 5 1 2 3 4 1 2 3 5 5 4 Figure 11.6-3

39. © 2010 Pearson Education, Inc. Eukaryotic mRNAs –Can last for hours to weeks to months –Are all eventually broken down and their parts recycled

40. © 2010 Pearson Education, Inc. microRNAs Small single-stranded RNA molecules, called microRNAs (miRNAs), bind to complementary sequences on mRNA molecules in the cytoplasm, and some trigger the breakdown of their target mRNA.

41. © 2010 Pearson Education, Inc. The Initiation of Translation The process of translation offers additional opportunities for regulation.

42. © 2010 Pearson Education, Inc. Protein Activation and Breakdown Post-translational control mechanisms –Occur after translation –Often involve cutting polypeptides into smaller, active final products Animation: Protein Processing Animation: Protein Degradation

43. Initial polypeptide Figure 11.7-1

44. Initial polypeptide Cutting Insulin (active hormone) Figure 11.7-2

45. © 2010 Pearson Education, Inc. The selective breakdown of proteins is another control mechanism operating after translation.

46. © 2010 Pearson Education, Inc. Cell Signaling In a multicellular organism, gene regulation can cross cell boundaries. A cell can produce and secrete chemicals, such as hormones, that affect gene regulation in another cell. Animation: Signal Transduction Pathways Animation: Overview of Cell Signaling Blast Animation: Signaling Across Membranes Animation: Cell Signaling Video: C. elegans Embryo Development (time lapse) Video: C. elegans Crawling

47. SIGNALING CELL Plasma membrane Signal molecule Secretion TARGET CELL Nucleus Figure 11.8-1

48. SIGNALING CELL Plasma membrane Signal molecule Secretion Receptor protein Reception TARGET CELL Nucleus Figure 11.8-2

49. SIGNALING CELL Plasma membrane Signal molecule Secretion Receptor protein Reception Signal transduction pathway TARGET CELL Nucleus Figure 11.8-3

50. SIGNALING CELL Plasma membrane Signal molecule Secretion Receptor protein Transcription factor (activated) Reception Signal transduction pathway TARGET CELL Nucleus Figure 11.8-4

51. SIGNALING CELL mRNA Plasma membrane Signal molecule Secretion Receptor protein Transcription factor (activated) Reception Signal transduction pathway TARGET CELL Nucleus Transcription Response Figure 11.8-5

52. SIGNALING CELL mRNA Plasma membrane Signal molecule Secretion Receptor protein Transcription factor (activated) Reception Signal transduction pathway TARGET CELL Nucleus Transcription Response Translation New protein Figure 11.8-6

53. © 2010 Pearson Education, Inc. Master control genes called homeotic genes regulate groups of other genes that determine what body parts will develop in which locations. Homeotic genes

54. © 2010 Pearson Education, Inc. Mutations in homeotic genes can produce bizarre effects.

55. Normal fruit fly Mutant fly with extra wings Normal head Mutant fly with extra legs growing from head Figure 11.9

56. Normal fruit fly Mutant fly with extra wings Figure 11.9a

57. Normal head Mutant fly with extra legs growing from head Figure 11.9b

58. © 2010 Pearson Education, Inc. Similar homeotic genes help direct embryonic development in nearly every eukaryotic organism. Animation: Development of Head-Tail Axis in Fruit Flies

59. Fruit fly chromosome Fruit fly embryo (10 hours) Mouse chromosomes Mouse embryo (12 days) Adult fruit flyAdult mouse Figure 11.10

60. Fruit fly chromosome Fruit fly embryo (10 hours) Adult fruit fly Figure 11.10a

61. Mouse chromosomes Mouse embryo (12 days) Adult mouse Figure 11.10b

62. © 2010 Pearson Education, Inc. DNA Microarrays: Visualizing Gene Expression A DNA microarray allows visualization of gene expression. The pattern of glowing spots enables the researcher to determine which genes were being transcribed in the starting cells. Researchers can thus learn which genes are active in different tissues or in tissues from individuals in different states of health.

63. mRNA isolated Figure 11.11-1

64. mRNA isolated cDNA made from mRNA Reverse transcriptase and fluorescently labeled DNA nucleotides Fluorescent cDNA Figure 11.11-2

65. mRNA isolated cDNA made from mRNA cDNA mixture added to wells DNA microarray Reverse transcriptase and fluorescently labeled DNA nucleotides Fluorescent cDNA Figure 11.11-3

66. mRNA isolated DNA of an expressed gene cDNA made from mRNA cDNA mixture added to wells Unbound cDNA rinsed away Fluorescent spot Fluorescent cDNA DNA of an unexpressed gene DNA microarray (6,400 genes) Nonfluorescent spot DNA microarray Reverse transcriptase and fluorescently labeled DNA nucleotides Fluorescent cDNA Figure 11.11-4

67. DNA microarray (6,400 genes) Figure 11.11a

68. CLONING PLANTS AND ANIMALS The Genetic Potential of Cells Differentiated cells –All contain a complete genome –Have the potential to express all of an organism’s genes Differentiated plant cells can develop into a whole new organism. © 2010 Pearson Education, Inc.

69. Root of carrot plant Figure 11.12-1

70. Root cells in growth medium Root of carrot plant Figure 11.12-2

71. Cell division in culture Root cells in growth medium Root of carrot plant Single cell Figure 11.12-3

72. Young plant Cell division in culture Root cells in growth medium Root of carrot plant Single cell Figure 11.12-4

73. Adult plant Young plant Cell division in culture Root cells in growth medium Root of carrot plant Single cell Figure 11.12-5

74. © 2010 Pearson Education, Inc. The somatic cells of a single plant can be used to produce hundreds of thousands of clones. Plant cloning –Demonstrates that cell differentiation in plants does not cause irreversible changes in the DNA –Is now used extensively in agriculture

75. © 2010 Pearson Education, Inc. Regeneration –Is the regrowth of lost body parts –Occurs, for example, in the regrowth of the legs of salamanders

76. © 2010 Pearson Education, Inc. Reproductive Cloning of Animals Nuclear transplantation –Involves replacing nuclei of egg cells with nuclei from differentiated cells –Has been used to clone a variety of animals

77. © 2010 Pearson Education, Inc. In 1997, Scottish researchers produced Dolly, a sheep, by replacing the nucleus of an egg cell with the nucleus of an adult somatic cell in a procedure called reproductive cloning, because it results in the birth of a new animal.

78. Remove nucleus from egg cell Figure 11.13-1

79. Donor cell Remove nucleus from egg cell Add somatic cell from adult donor Figure 11.13-2

80. Donor cell Nucleus from donor cell Remove nucleus from egg cell Add somatic cell from adult donor Grow in culture to produce an early embryo Figure 11.13-3

81. Donor cell Nucleus from donor cell Remove nucleus from egg cell Add somatic cell from adult donor Grow in culture to produce an early embryo Implant embryo in surrogate mother Clone of donor is born Reproductive cloning Figure 11.13-4

82. Donor cell Nucleus from donor cell Remove nucleus from egg cell Add somatic cell from adult donor Grow in culture to produce an early embryo Remove embryonic stem cells from embryo and grow in culture Induce stem cells to form specialized cells for therapeutic use Implant embryo in surrogate mother Clone of donor is born Reproductive cloning Therapeutic cloning Figure 11.13-5

83. Figure 11.13a

84. © 2010 Pearson Education, Inc. Other mammals have since been produced using this technique including –Farm animals –Control animals for experiments –Rare animals in danger of extinction Practical Applications of Reproductive Cloning

85. (a) The first cloned cat (right) Figure 11.14a

86. (b) Cloning for medical use Figure 11.14b

87. © 2010 Pearson Education, Inc. Human Cloning Cloning of animals –Has heightened speculation about human cloning –Is very difficult and inefficient Critics raise practical and ethical objections to human cloning.

88. (c) Clones of endangered animals Gray wolf Gaur Banteng Mouflon calf with mother Figure 11.14c

89. (a) The first cloned cat (right) (c) Clones of endangered animals (b) Cloning for medical use Gray wolf Gaur Banteng Mouflon calf with mother Figure 11.14

90. © 2010 Pearson Education, Inc. Therapeutic Cloning and Stem Cells The purpose of therapeutic cloning is not to produce a viable organism but to produce embryonic stem cells.

91. © 2010 Pearson Education, Inc. Embryonic Stem Cells Embryonic stem cells (ES cells) –Are derived from blastocysts –Can give rise to specific types of differentiated cells

92. © 2010 Pearson Education, Inc. Adult stem cells –Are cells in adult tissues –Generate replacements for nondividing differentiated cells Unlike embryonic ES cells, adult stem cells –Are partway along the road to differentiation –Usually give rise to only a few related types of specialized cells Adult Stem Cells Blast Animation: Stem Cells

93. Adult stem cells in bone marrow Cultured embryonic stem cells Different culture conditions Different types of differentiated cells Heart muscle cells Nerve cells Blood cells Figure 11.15

94. © 2010 Pearson Education, Inc. Umbilical Cord Blood Banking Umbilical cord blood –Can be collected at birth –Contains partially differentiated stem cells –Has had limited success in the treatment of a few diseases

95. Figure 11.16

96. © 2010 Pearson Education, Inc. THE GENETIC BASIS OF CANCER In recent years, scientists have learned more about the genetics of cancer.

97. © 2010 Pearson Education, Inc. Genes That Cause Cancer As early as 1911, certain viruses were known to cause cancer. Oncogenes are –Genes that cause cancer –Found in viruses

98. © 2010 Pearson Education, Inc. Oncogenes and Tumor-Suppressor Genes Proto-oncogenes are –Normal genes with the potential to become oncogenes –Found in many animals –Often genes that code for growth factors, proteins that stimulate cell division

99. © 2010 Pearson Education, Inc. For a proto-oncogene to become an oncogene, a mutation must occur in the cell’s DNA.

100. New promoter Normal growth- stimulating protein in excess Normal growth- stimulating protein in excess Hyperactive growth- stimulating protein Gene moved to new DNA position, under new controls Multiple copies of the gene DNA Mutation within the gene Proto-oncogene (for protein that stimulates cell division) Oncogene Figure 11.17

101. © 2010 Pearson Education, Inc. Tumor-suppressor genes –Inhibit cell division –Prevent uncontrolled cell growth –May be mutated and contribute to cancer

102. Defective, nonfunctioning protein Cell division under control (b) Uncontrolled cell growth (cancer) Normal growth- inhibiting protein Cell division not under control (a) Normal cell growth Tumor-suppressor gene Mutated tumor-suppressor gene Figure 11.18

103. Cell division under control Normal growth- inhibiting protein (a) Normal cell growth Tumor-suppressor gene Figure 11.18a

104. Defective, nonfunctioning protein (b) Uncontrolled cell growth (cancer) Cell division not under control Mutated tumor-suppressor gene Figure 11.18b

105. The Process of Science: Can Cancer Therapy Be Personalized? Observations: Specific mutations can lead to cancer. Question: Can this knowledge be used to help patients with cancer? Hypothesis: DNA sequencing technology can be used to test tumors and identify which cancer-causing mutations they carry. © 2010 Pearson Education, Inc.

106. Experiment: Researchers screened for 238 possible mutations in 1,000 human tumors from 18 different body tissues. Results: –No mutations are present in every tumor. –Each tumor involves different mutations. –It is possible to cheaply and accurately determine which mutations are present in a given cancer patient.

107. Table 11.1

108. © 2010 Pearson Education, Inc. The Progression of a Cancer Over 150,000 Americans will be stricken by cancer of the colon or rectum this year. Colon cancer –Spreads gradually –Is produced by more than one mutation

109. Oncogene activated DNA changes: Cellular changes: Increased cell division Figure 11.19-1

110. Tumor-suppressor gene inactivated Oncogene activated DNA changes: Cellular changes: Increased cell division Growth of benign tumor Colon wall Figure 11.19-2

111. Second tumor-suppressor gene inactivated Tumor-suppressor gene inactivated Oncogene activated DNA changes: Cellular changes: Increased cell division Growth of benign tumor Growth of malignant tumor Colon wall Figure 11.19-3

112. © 2010 Pearson Education, Inc. The development of a malignant tumor is accompanied by a gradual accumulation of mutations that –Convert proto-oncogenes to oncogenes –Knock out tumor-suppressor genes

113. Normal cell Chromosomes Figure 11.20-1

114. 1 mutation Normal cell Chromosomes Figure 11.20-2

115. 1 mutation Normal cell 2 mutations Chromosomes Figure 11.20-3

116. 1 mutation Normal cell 3 mutations 2 mutations Chromosomes Figure 11.20-4

117. 1 mutation Normal cell Malignant cell 4 mutations 3 mutations 2 mutations Chromosomes Figure 11.20-5

118. © 2010 Pearson Education, Inc. “Inherited” Cancer Most mutations that lead to cancer arise in the organ where the cancer starts. In familial or inherited cancer –A cancer-causing mutation occurs in a cell that gives rise to gametes –The mutation is passed on from generation to generation

119. © 2010 Pearson Education, Inc. Breast cancer –Is usually not associated with inherited mutations –In some families can be caused by inherited, BRCA1 cancer genes

120. Figure 11.21

121. © 2010 Pearson Education, Inc. Cancer Risk and Prevention Cancer –Is one of the leading causes of death in the United States –Can be caused by carcinogens, cancer-causing agents found in the environment, including –Tobacco products –Alcohol –Exposure to ultraviolet light from the sun

122. Table 11.2

123. © 2010 Pearson Education, Inc. Exposure to carcinogens –Is often an individual choice –Can be avoided Some studies suggest that certain substances in fruits and vegetables may help protect against a variety of cancers.

124. Evolution Connection: The Evolution of Cancer in the Body Evolution drives the growth of a tumor. Like individuals in a population of organisms, cancer cells in the body –Have the potential to produce more offspring than can be supported by the environment –Show individual variation, which –Affects survival and reproduction –Can be passed on to the next generation of cells © 2010 Pearson Education, Inc.

125. Figure 11.22

126. Figure 11.UN01

127. Figure 11.UN02

128. Figure 11.UN03

129. Figure 11.UN04

130. Regulatory gene A typical operon Promoter Operator Gene 3 Gene 2 Gene 1 Switches operon on or off RNA polymerase binding site Produces repressor that in active form attaches to operator DNA Figure 11.UN05

131. Protein breakdown Protein activation mRNA breakdown RNA transport Translation Transcription DNA unpacking RNA processing Figure 11.UN06

132. Nucleus from donor cell Embryo implanted in surrogate mother Clone of nucleus donor Early embryo resulting from nuclear transplantation Figure 11.UN07

133. Nucleus from donor cell Embryonic stem cells in culture Specialized cells Early embryo resulting from nuclear transplantation Figure 11.UN08

134. Proto-oncogene (normal) Oncogene Mutation Normal protein Mutant protein Defective protein Mutation Normal regulation of cell cycle Normal growth-inhibiting protein Out-of-control growth (leading to cancer) Mutated tumor-suppressor gene Tumor-suppressor gene (normal) Figure 11.UN09