Chapter 8 Genetically Modified Organisms Gene Expression Mutation

Chapter 8 § Genetically Modified Organisms § Gene Expression, Mutation, and Cloning Copyright © 2010 Pearson Education, Inc.

Chapter 8 Section 1 Protein Synthesis and Gene Expression Part A: Transcription Copyright © 2010 Pearson Education, Inc.

Genetic Engineering § Alteration of hereditary traits by molecular biological techniques § One or more genes may be modified § Genes may be moved from one organism to another § Move a gene that produces a desired protein from one organism to another § Alter regulation of gene expression § Change the amount of protein that a gene produces Copyright © 2010 Pearson Education, Inc.

Genetic Engineering Controversy § Benefits: § Potential to wipe out hunger by make crops more productive § Vaccinate children by eating foods § Reduce heart problems by added omega-3 fatty acids to animals like pigs § Concerns: § Is it ethical? § Is it safe for use in food sources? § Will it be used in humans? Copyright © 2010 Pearson Education, Inc.

8. 1 Protein Synthesis and Expression History of Genetic Engineering § In the early 1980 s, genetic engineers at Monsanto® Company began producing recombinant bovine growth hormone (r. BGH) § Made by genetically engineered bacteria § The bacteria were given DNA that carries instructions for making BGH § Giving growth hormone to cows increase body size and milk production Copyright © 2010 Pearson Education, Inc.

8. 1 Protein Synthesis and Expression How do genes make proteins? Protein synthesis § the process of using instructions carried on a gene to create proteins. § Gene – a sequence of DNA that encodes a protein § Protein – a large molecule composed of amino acids § Several steps are involved and require both DNA and RNA. Copyright © 2010 Pearson Education, Inc.

8. 1 Protein Synthesis and Expression Structure of DNA & RNA DNA § Double-stranded § Each nucleotide composed of deoxyribose, phosphate, and nitrogenous base § 4 bases: adenine, thymine, guanine, cytosine Copyright © 2010 Pearson Education, Inc.

8. 1 Protein Synthesis and Expression Structure of DNA & RNA § Single-stranded § Nucleotides comprised of ribose, phosphate, and nitrogenous base § 4 bases: A, C, G, and Uracil Copyright © 2010 Pearson Education, Inc.

8. 1 Protein Synthesis and Expression: From Gene to Protein § The flow of genetic information in a cell is DNA RNA protein Copyright © 2010 Pearson Education, Inc. Figure 8. 2

8. 1 Protein Synthesis and Expression: From Gene to Protein § There are 2 steps in going from gene to protein § Transcription (DNA RNA) § Translation (RNA Protein) Copyright © 2010 Pearson Education, Inc.

8. 1 Protein Synthesis and Expression: Transcription § Transcription occurs in the nucleus. § RNA polymerase binds to the promoter region of the gene. § RNA polymerase zips down the length of gene, matching RNA nucleotides with complementary DNA nucleotides Copyright © 2010 Pearson Education, Inc.

8. 1 Protein Synthesis and Expression: Transcription § The product of transcription is messenger RNA (m. RNA). Copyright © 2010 Pearson Education, Inc.

8. 1 Protein Synthesis and Expression: Transcription PLAY Animation—Transcription Copyright © 2010 Pearson Education, Inc.

Chapter 8 Section 1 Protein Synthesis and Gene Expression End Part A: Transcription Copyright © 2010 Pearson Education, Inc.

Chapter 8 Section 1 Protein Synthesis and Gene Expression Part B: Translation and the Genetic Code Copyright © 2010 Pearson Education, Inc.

8. 1 Protein Synthesis and Expression: Translation § Uses m. RNA template to make protein § Translation occurs in the cytoplasm § Translation requires: § § § m. RNA amino acids ATP Ribosomes Transfer RNA (t. RNA) Copyright © 2010 Pearson Education, Inc.

8. 1 Protein Synthesis and Expression: Translation Ribosomes § The ribosome is composed of r. RNA and comprises a small and a large subunit. § When subunits come together, m. RNA can be threaded between them to make protein § Also requires transfer RNA (t. RNA) to bring correct amino acids Copyright © 2010 Pearson Education, Inc. Large subunit Small subunit Figure 8. 4

8. 1 Protein Synthesis and Expression: Translation Transfer RNA (t. RNA ) § Each t. RNA carries one specific amino acids and matches its anticodon with codons on m. RNA § So what are codons and anticodons? ? Copyright © 2010 Pearson Education, Inc. Amino acid Binding site for amino acid Region of internal complementarity t. RNA Anticodon m. RNA Codon Figure 8. 5

8. 1 Protein Synthesis and Expression: Translation As ribosome moves along m. RNA, small sequences of nucleic acids are exposed § Codon – a three letter genetic code of nucleic acids in m. RNA that indicate a specific amino acid § Anticodon – a complementary three nucleic acid sequence on t. RNA that matches codon § >By using anticodons to match codons, t. RNA can bring the correct amino acid Copyright © 2010 Pearson Education, Inc. Figure 8. 5

8. 1 Protein Synthesis and Expression: Genetic Code The genetic code § The use of nucleic acid codons to specify amino acid sequence in proteins § A codon is comprised of three nucleotides = 64 possible combinations (43 combinations) § 61 codons code for ~20 amino acids § Redundancy – may be more than 1 code per amino acid § 3 others are stop codons, which end protein synthesis Copyright © 2010 Pearson Education, Inc.

8. 1 Protein Synthesis and Expression: Genetic Code Copyright © 2010 Pearson Education, Inc. Table 8. 1

8. 1 Protein Synthesis and Expression: Translation A protein is put together one amino acid at a time. 1. The ribosome attaches to the m. RNA at the promoter region. 2. Ribosome facilitates the docking of t. RNA anticodons to m. RNA codons. 3. When two t. RNAs are adjacent, a bond is formed between their amino acids. Copyright © 2010 Pearson Education, Inc.

8. 1 Protein Synthesis and Expression: Translation Step by Step 1 Amino acids and t. RNAs float freely in the cytoplasm. 2 Enzymes facilitate the binding of a specific t. RNA to its appropriate amino acid. Copyright © 2010 Pearson Education, Inc. Amino acid t. RNA Figure 8. 7

8. 1 Protein Synthesis and Expression: Translation 3 A t. RNA will dock if the complementary RNA codon is present on the ribosome. val r se ala 4 The amino acids join together to form a polypeptide. U Amino acid chain (polypeptide) AG arg ala phe ile GG C UCC Stop codon AAA UAU GCCUUUAUA Ribosome Copyright © 2010 Pearson Education, Inc. Figure 8. 7

8. 1 Protein Synthesis and Expression: Translation Amino acid chain (polypeptide) arg ala phe ile UCC GG C Stop codon AAA UAU GCCUUUAUA 5 The ribosome moves on to the next codon to receive the next t. RNA. Copyright © 2010 Pearson Education, Inc. Ribosome 6 When the ribosome reaches the stop codon, no t. RNA can basepair with the codon on the m. RNA and the newly synthesized protein are released. Figure 8. 7

8. 1 Protein Synthesis and Expression: Translation 7 The chain of amino acids folds, and the protein is ready to perform its job. GAG Protein (such as BGH) Copyright © 2010 Pearson Education, Inc. AGC STOP CUCUCGUAA 8 The subunits of the ribosome separate but can reassemble and begin translation of another m. RNA. Figure 8. 7

8. 1 Protein Synthesis and Expression: Translation PLAY Animation—Translation Copyright © 2010 Pearson Education, Inc.

Chapter 8 Section 1 Protein Synthesis and Gene Expression END Part B: Translation and the Genetic Code Copyright © 2010 Pearson Education, Inc.

Chapter 8 Section 1 Protein Synthesis and Gene Expression Part C: Types of Mutations and Regulating Gene Expression Copyright © 2010 Pearson Education, Inc.

8. 1 Protein Synthesis and Expression: Mutations = Changes in genetic sequence § Changes in genetic sequence might affect the order of amino acids in a protein. § Protein function is dependent on the precise order of amino acids Copyright © 2010 Pearson Education, Inc.

8. 1 Protein Synthesis and Expression: Mutation Possible outcomes of mutation: 1 - no change in protein (neutral mutation) 2 - non-functional protein 3 - different protein Copyright © 2010 Pearson Education, Inc. Figure 8. 8

8. 1 Protein Synthesis and Expression: Mutation Types of Mutations 1. Base-substitution mutation – simple substitution of one base for another 2. Frameshift mutation – addition or deletion of a base, which changes the reading frame Copyright © 2010 Pearson Education, Inc.

8. 1 Protein Synthesis and Expression Examples of Mutations • Neutral Mutation • Frameshift Mutation - adding or deleting a nucleic acid - shifts entire sequence Copyright © 2010 Pearson Education, Inc. Figure 8. 9

8. 1 Protein Synthesis and Expression: Overview of Gene Expression § Each cell in your body (except sperm and egg cells) has the same DNA. § But each cell only expresses a small percentage of genes. Copyright © 2010 Pearson Education, Inc.

8. 1 Protein Synthesis and Expression: An Overview of Gene Expression § Regulating gene expression § Turning a gene or a set of genes on or off § EXP: Nerves and muscles have the same suite of genes, but express different genes. Copyright © 2010 Pearson Education, Inc. Figure 8. 11

8. 1 Protein Synthesis and Expression: § Regulating gene expression 1. Repression of transcription Copyright © 2010 Pearson Education, Inc. Figure 8. 11

8. 1 Protein Synthesis and Expression: § Regulating gene expression 2. Activation of transcription Copyright © 2010 Pearson Education, Inc. Figure 8. 11

Chapter 8 Section 1 Protein Synthesis and Gene Expression Part C: Types of Mutations and Regulating Gene Expression Copyright © 2010 Pearson Education, Inc.

Chapter 8 Section 2 Producing Recombinant Proteins Copyright © 2010 Pearson Education, Inc.

8. 2 Producing Recombinant Proteins: Cloning a Gene Using Bacteria Producing Recombinant Proteins § BGH is a protein, and is coded by a specific gene. § Transfer of BGH gene to bacteria allows for growth under ideal conditions. § Bacteria can serve as “factories” for production of BGH. Copyright © 2010 Pearson Education, Inc.

8. 2 Producing Recombinant Proteins: Cloning a Gene Using Bacteria Two Important molecules in cloning 1. Restriction enzymes 2. Plasmids Copyright © 2010 Pearson Education, Inc.

8. 2 Producing Recombinant Proteins: Cloning a Gene Using Bacteria Restriction enzymes § Used by bacteria as a form of defense. § Restriction enzymes cut DNA at specific sequences. § Leave “sticky ends” § They are important in biotechnology because they allow scientists to make precise cuts in DNA. Copyright © 2010 Pearson Education, Inc.

8. 2 Producing Recombinant Proteins: Cloning a Gene Using Bacteria Plasmid § Small, circular piece of bacterial DNA that exists separate from the bacterial chromosome. § Plasmids are important because they can act as a ferry to carry a gene into a cell. Copyright © 2010 Pearson Education, Inc.

8. 2 Producing Recombinant Proteins: Steps in Cloning a Gene Using Bacteria § Step 1. Remove the gene from the cow chromosome using restriction enzymes 1 BGH gene is cut from the cow chromosome using restriction enzymes that leave “sticky ends” with specific base sequences. Cow cell BGH gene DNA Copyright © 2010 Pearson Education, Inc. Figure 8. 13

8. 2 Producing Recombinant Proteins: Cloning a Gene Using Bacteria § Step 2. Insert the BGH gene into the bacterial plasmid Copyright © 2010 Pearson Education, Inc. Figure 8. 13

8. 2 Producing Recombinant Proteins: Cloning a Gene Using Bacteria § Recombinant – Indicates material that has been genetically engineered. A gene that has been removed from its original genome and combined with another. § After step 2, the BGH is now referred to as recombinant BGH or r. BGH. Copyright © 2010 Pearson Education, Inc.

8. 2 Producing Recombinant Proteins: Cloning a Gene Using Bacteria § Step 3. Insert the recombinant plasmid into a bacterial cell Recombinant plasmid 3 The recombinant plasmid is reinserted into a bacterial cell. The plasmids and the bacterial cells replicate, making millions of copies of the r. BGH gene. r. BGH proteins The r. BGH genes produce large quantities of r. BGH proteins that are harvested, purified, and injected into cows to increase milk production. Copyright © 2010 Pearson Education, Inc. Figure 8. 13

8. 2 Producing Recombinant Proteins PLAY Animation—Producing Bovine Growth Hormone Copyright © 2010 Pearson Education, Inc.

8. 2 Producing Recombinant Proteins Use of r. BGH in Agriculture § About 1/3 of cows in the US are injected with r. BGH. § r. BGH increases milk volume from cows by about 20%. § Increase profits for both ranchers and industry Copyright © 2010 Pearson Education, Inc.

8. 2 Producing Recombinant Proteins Controversy over Use of r. BGH § Controversy over safety to humans § USDA and Monsanto argue that milk from r. BGH-treated cows is indistinguishable from non-treated. § Activists disagree. Welfare of cows? Europe and Canada banned r. BGH over concerns on the health of cows. Copyright © 2010 Pearson Education, Inc.

8. 2 Producing Recombinant Proteins: Cloning a Gene Using Bacteria The same principles apply to other proteins § Clotting proteins for hemophiliacs are produced using similar methods. § Insulin for diabetics is also produced in this way. Copyright © 2010 Pearson Education, Inc.

END Chapter 8 Section 2 Producing Recombinant Proteins Copyright © 2010 Pearson Education, Inc.

Chapter 8 Section 3 Genetically Modified Foods Copyright © 2010 Pearson Education, Inc.

8. 3 Genetically Modified Foods Artificial Selection § All agricultural products are the result of genetic modification through selective breeding. § Artificial selection does not move genes from one organism to another, but does drastically change the characteristics of a population. Copyright © 2010 Pearson Education, Inc. Figure 8. 13

8. 3 Genetically Modified Foods: Why Genetically Modify Crop Plants? § Increase shelf life, yield, or nutritional value § Exp: Golden rice has been genetically engineered to produce beta-carotene, which increases the rice’s nutritional yield. Copyright © 2010 Pearson Education, Inc. Figure 8. 16

8. 3 Genetically Modified Foods: Modifying Plants with the Ti Plasmid and Gene Gun Modifying Plants Directly § (Different than r. BGH, which was a protein injected into cows) § In order to do this, the target gene must be inserted into the plant cell. § Two methods can inject genes into plants: 1. Ti plasmid 2. Gene gun Copyright © 2010 Pearson Education, Inc.

8. 3 Genetically Modified Foods: Modifying Plants with the Ti Plasmid and Gene Gun Modifying Plants wiith the Ti plasmid § To modify the plant, must gene across cell wall § The bacterium Agrobacterium tumefaciens does this naturally, creating ‘galls’ • The bacterium can do this by using the Ti plasmid Copyright © 2010 Pearson Education, Inc.

8. 3 Genetically Modified Foods: Modifying Plants wiith the Ti plasmid Copyright © 2010 Pearson Education, Inc. Figure 8. 17 b

8. 3 Genetically Modified Foods: Modifying Plants with the Ti Plasmid and Gene Gun § The Gene Gun Microscopic particles coated with gene of interest are “shot” into plant cells. Gun Shock waves “Bullet” Plant cells in culture Copyright © 2010 Pearson Education, Inc. Figure 8. 18

8. 3 Genetically Modified Foods: Transgenic organism § the result is the incorporation of a gene from one organism to the genome of another. § Also referred to as a Genetically Modified Organism (GMO). Copyright © 2010 Pearson Education, Inc.

8. 3 Genetically Modified Foods: Effect of GM Crops and the Environment Benefits § Crops can be engineered for resistance to pests, thus farmers can spray fewer chemicals. Concerns § GM crops may actually lead to increased use of pesticides and herbicides. § EXP: Roundup-Ready plants § GM crop plants may transfer genes to wild relatives. Copyright © 2010 Pearson Education, Inc.

End Chapter 8 Section 3 Genetically Modified Foods Copyright © 2010 Pearson Education, Inc.

Chapter 8 Section 4 Genetically Modified Humans Copyright © 2010 Pearson Education, Inc.

8. 4 Genetically Modified Humans: Stem Cells Genetically Modified Humans § Stem cells: § undifferentiated cells § Totipotent = capable of growing into many different kinds of cells and tissues. Copyright © 2010 Pearson Education, Inc. Figure 8. 20

8. 4 Genetically Modified Humans: Stem Cells Use of Stem cells § Stem cells can be collected, with consent, from left over embryos from artificial fertilization § Cells can be grown ‘in vitro’ in the lab § Can be ‘directed’ to develop into many different kinds of tissues Copyright © 2010 Pearson Education, Inc.

8. 4 Genetically Modified Humans: Stem Cells Therapeutic Cloning § Stems cells might be used to treat degenerative diseases § Alzheimer’s or Parkinson’s, multiple sclerosis, or liver, lung, or heart disease. § Stem cells could also be used to grow specific tissues § to treat burns, heart attack damage, replacement cartilage in joints, or spinal cord injuries. Copyright © 2010 Pearson Education, Inc.

8. 4 Genetically Modified Humans: Human Genome Project § international effort to map the sequence of the entire human genome (~20, 000 – 25, 000 genes). § A genome is all of the genes in an organism § For comparative purposes, genomes of other model organisms (E. coli, yeast, fruit flies, mice) were also mapped. Copyright © 2010 Pearson Education, Inc.

8. 4 Genetically Modified Humans: Gene Therapy = replacement of defective genes with functional genes Two approaches: 1. Germ line gene therapy 2. Somatic cell gene therapy Copyright © 2010 Pearson Education, Inc.

8. 4 Genetically Modified Humans: Gene Therapy Germ line gene therapy § Embryonic treatment § Embryo supplied with a functional version of the defective gene. § Embryo + cells produced by cell division have a functional version of gene. § Including their children § > would prevent genetic diseases Copyright © 2010 Pearson Education, Inc.

8. 4 Genetically Modified Humans: Gene Therapy Somatic cell gene therapy § fix or replace the defective protein only in specific cells. § Performed on adult body cells § Put copy of good gene into cells in lab, multiply cells, then introduce to affected person § Already used as a treatment of SCID (severe combined immunodeficiency) Copyright © 2010 Pearson Education, Inc.

8. 4 Genetically Modified Humans: Gene Therapy Copyright © 2010 Pearson Education, Inc.

8. 4 Genetically Modified Humans: Cloning Humans § Cloning = making a genetically identical organism § Cloning occurs naturally whenever identical twins are produced. § Cloning of offspring from adults has already been done with cattle, goats, mice, cats, pigs, and sheep. § Cloning is achieved through the process of NUCLEAR TRANSFER. Copyright © 2010 Pearson Education, Inc.

8. 4 Genetically Modified Humans: Cloning Dolly the Sheep Copyright © 2010 Pearson Education, Inc.

8. 4 Genetically Modified Humans: Cloning Humans § Genetic engineering is controversial. Copyright © 2010 Pearson Education, Inc. Table 8. 2

END Chapter 8 Section 4 Genetically Modified Humans Copyright © 2010 Pearson Education, Inc.

END Chapter 8 Copyright © 2010 Pearson Education, Inc.