Chapter 5: DNA, Gene Expression, and Biotechnology

Transcription

1 Announcements Exam on Tuesday! 50 Questions, similar to those on PS 1 and 2. Review Session Saturday 4-6PM in Center 101. Now will focus only on Chapters 1-4! Chapter 5: DNA, Gene Expression, and Biotechnology Thursday is our first debate. The topic is Genetically modified foods are safe. Please sign up after class if you d like to participate. We will have 6 students per side. Those not participating directly will write a short (2 pages or less) paper describing the Pros vs. Cons of GMOs and stating your position on whether you feel they are safe or not. What is the genetic code, and how is it harnessed? Lecture 5 Outline I. DNA A. What is it? B. What does it do? II. Genes A. What are they? B. Transcription C. Translation D. Mutation III. Biotechnology A. What is it? B. Toolbox C. Potential to aid human health D. GMOs

2 DNA Double Helix Nucleic acids and nucleotides Sugars, Phosphates, and Bases A, T, C, and G base pairs The DNA molecule contains instructions for the development and functioning of all living organisms.

3 Evolu&on of the Gene&c Code The gene&c code is nearly universal, from bacteria to animals. Genes can be transcribed and translated a<er being transferred from one species into another. A firefly gene expressed in a plant! The DNA 200 Knowledge about DNA is increasing justice in the world. Julius Ruffin s case is tragic, but it is not unusual. He is one of a group of 200 people who have been freed from prison as a result of DNA analyses. Called The DNA 200, these unjustly imprisoned people spent an average of 12 years behind bars. Eighty- percent had been convicted of sexual assault, 28% were convicted of murder. In more than three- quarters of the cases, inaccurate eyewitness tes5mony played an important role in the guilty verdict.

4 Genes are sections of DNA that contain instructions for making proteins. The number of chromosomes varies from species to species. q Corn has 10 unique chromosomes. q Fruit flies have only four. q Dogs and chickens have 39 different chromosomes. Genes q A sequence of bases in a DNA molecule that carries the information necessary for producing a functional product, usually a protein molecule or RNA q Goldfish have 47 chromosomes. q Individuals in each of these species inherit one copy of each chromosome from each parent.

5 Not all DNA contains instructions for making proteins. Insert figure 5-8 The Proportion of the DNA That Codes for Genes

6 Introns q Non-coding regions of DNA q May take the form of short (or long) sequences that are repeated thousands of times How do genes work? An overview q May also consist of gene fragments, duplicate versions of genes, and pseudogenes q Genotype All of the genes contained in an organism The Central Dogma: DNA RNA Protein Prokaryotes Eukaryotes Nuclear envelope q Phenotype The physical manifestations of the instructions TRANSCRIPTION TRANSLATION DNA Polypeptide Without nucleus, simultaneous transcription and translation mrna Ribosome TRANSCRIPTION RNA PROCESSING TRANSLATION mrna DNA Pre-mRNA Polypeptide Ribosome With nucleus, transcription and translation separated and requires RNA processing

7 Transcription: Reading the information coded in DNA Transcrip&on

8 Several ingredients must be present in the cytoplasm for translation to occur: In translation, the mrna copy of the information from DNA is used to build functional molecules. q Free amino acids q Ribosomal units q Transfer RNA The Genetic Code Insert figure 5-14

9 Transla&on Insert figure 5-15 Controlling Gene Expression Cells turn genes on and off in several ways. Gene expression and gene regulation q Transcription factors Proteins that bind to specific regulatory sites on the DNA q Positive control q Negative control

10 Prokaryotic Gene Control and the lac Operon Insert figure 5-17 Eukaryotic Gene Control q There are many other ways that genes can be regulated besides operons. q Transcription Regulation Activators and repressors Enhancer sequences Chemical interference Damage to the genetic code has a variety of causes and effects. q Post-Transcription Regulation

11 Muta&ons can affect protein structure & func&on Muta&ons changes in the gene&c material of a cell Point muta&ons are changes in just one base pair of a gene Muta&ons can affect protein structure & func&on Abnormal proteins can result from single nucleo&de changes Wild-type hemoglobin DNA Mutant hemoglobin DNA C T T C A T mrna mrna G A A G U A Normal hemoglobin Glu Sickle-cell hemoglobin Val

12 Abnormal proteins can result from single nucleo&de changes From mutation to illness in just four steps: 1. A mutated gene codes for a nonfunctioning protein, usually an enzyme. 2. The non-functioning enzyme can t catalyze the reaction as it normally would, bringing it to a halt. From mutation to illness in just four steps: 3. The molecule with which the enzyme would have reacted accumulates, like a blocked assembly line. 4. The accumulating chemical causes sickness and/or death.

13 Phenylketonuria Rare genetic condition where one is lacking enzyme to break down AA Phenylalanine Biotechnology Biotechnology is producing improvements in agriculture. Insert section opener photo What is biotechnology? Genetic engineering q Adding, deleting, or transplanting genes from one organism to another, to alter the organisms in useful ways Insert figure 5-24

14 Restriction Enzymes Insert figure 5-25 Insert figure 5-26 Insert figure 5-27

15 Insert figure 5-28 Insert figure 5-29 Biotechnology can improve food nutrition and make farming more efficient and ecofriendly. Insert figure 5-30 How might a genetically modified plant help 500 million malnourished people? Nutrient-rich golden rice

16 Almost everyone in the United States consumes genetically modified foods regularly without knowing it. What foods are responsible for this? Insect Resistance How can genetically modified plants lead to reduced pesticide use by farmers? Insert figure 5-33

17 Herbicide Resistance Faster Growth and Bigger Bodies q The ecological and health risks of such widespread use of transgenic species are not fully understood and are potentially great.

18 Fears and risks: Are genetically modified foods safe? q Fear #1. Organisms that we want to kill may become invincible. q Fear #2. Organisms that we don t want to kill may be killed inadvertently. q Fear #3. Genetically modified crops are not tested or regulated adequately. The treatment of diseases and production of medicines are improved with biotechnology. q Preventing diseases q Curing diseases q Fear #4. Eating genetically modified foods is dangerous. q Fear #5. Loss of genetic diversity among crop plants is risky. q Fear #6. Hidden costs may reduce the financial advantages of genetically modified crops. q Treating diseases The treatment of diabetes

19 Several important achievements followed the development of insulin-producing bacteria, including: Insert figure Human growth hormone (HGH) 2. Erythropoietin Gene therapy: Biotechnology can help diagnose and prevent diseases. 1. Is a given set of parents likely to produce a baby with a genetic disease? But has had a limited success in curing them Insert figure 5-41

20 2. Will a baby be born with a genetic disease? q Cystic fibrosis - 1/25 people are carriers! 3. Is an individual likely to develop a genetic disease later in life? q Breast cancer q Sickle-cell anemia q Down syndrome q Prostate cancer q Skin cancer q Others Ethical Dilemmas q Discrimination q Health insurance Insert figure 5-42 q How to proceed with the information?

21 Gene Therapy Difficulties Why has gene therapy had such a poor record of success in curing diseases? 1. Difficulty getting the working gene into the specific cells where it is needed 2. Difficulty getting the working gene into enough cells and at the right rate to have a physiological effect Gene Therapy Difficulties 3. Difficulty arising from the transfer organism getting into unintended cells 4. Difficulty regulating gene expression Cloning ranging from genes to organs to individuals offers both promise and perils.

22 DNA as an individual identifier: the uses of DNA fingerprinting Insert figure 5-45c

23 Insert figure 5-46 What is a DNA fingerprint? DNA and Biotechnology: Reading: Chapter 5 Sign up now if interested in participating in Debate! Animations from Today s lecture can be found at: