CHAPTER 15 GENETIC ENGINEERING Section 15 1 Selective

CHAPTER 15: GENETIC ENGINEERING Section 15 -1: Selective Breeding

Selective Breeding � � � When humans allow only organisms with “wanted” or “desired” characteristics to produce the next generation Technique used for thousands of years to produce new varieties of cultivated plants and domesticated animals Two methods: hybridization and inbreeding

Hybridization � � � Crossing dissimilar individuals to bring together the best characteristics of both organisms Hybrids often hardier than either parent Example: crossing a disease resistant plant with one that produces a lot of food

Inbreeding � � Continued breeding of individuals with similar characteristics Maintains desirable characteristics in a line of organisms Example: pure bred dogs and cats Can be risky – higher chance of recessive alleles pairing, genetic defects

Increasing Variation � � Scientists who manipulate organisms’ genetic makeup are using biotechnology – the application of a technological process , invention, or method to living organisms Types of biotechnology include selective breeding, increasing mutation rates, using drugs to create polyploid plants, and others

Bacterial Mutations � � � Using radiation or chemicals (mutagens) can increase the rate of mutation Breeders can create mutants with beneficial characteristics Example: oil digesting mutant bacterial strains are used to help clean up oil spills; working on bacteria that can clean up radioactive substances or metal pollution

Polyploid Plants � � Drugs that prevent chromosome separation in meiosis are useful in plant breeding, to create polyploid plants that are larger and stronger than the normal diploids Many important crop plants are polyploid

CHAPTER 13 – RECOMBINANT DNA AND GENETIC ENGINEERING College Prep Biology Mr. Martino

Introduction � Gene Therapy: transfer of one or more modified genes into an individual’s cells � Correct genetic defect � Boost immune system � Recombinant DNA Technology: science of cutting and recombining DNA from different species � Genes are then placed into bacterial, yeast or mammalian cells and replicated � Genetic Engineering: genes are isolated, modified, and inserted back into a cell � also called biotechnology

15. 1 Making Recombinant DNA Restriction enzyme: enzyme that chops up DNA at a specific sequence Bacterial Viral defense mechanism May cut a DNA strand a few times Helpful in studying DNA Produces “sticky ends” which may pair with other DNA Genome: all the DNA in a haploid number of chromosomes for each species

Plasmids: small circle of DNA In bacterial cells Insert foreign DNA (gene) into and put back in bacteria – reproduces naturally making a DNA clone Cloning vector: plasmid used to accept foreign DNA and replicate it Reverse transcriptase: enzyme from RNA viruses that perform transcription in reverse (RNA to DNA) c. DNA: (copied DNA) mature m. RNA transcript that has already been spliced Bacteria cannot remove introns and splice exons Reverse transcriptase makes DNA from m. RNA to insert into plasmid

15. 2 PCR – Polymerase Chain Reaction PCR: a fast method of amplifying (making lots of copies) DNA isolated, mixed with DNA polymerase, nucleotides, and some other good stuff Produces 2 daughters Daughters replicate, etc. 1 DNA molecule generates 100 billion in a few hours Used in evolution research, analyze DNA from fossils, analyze embryos, court cases

15. 3 DNA Fingerprints No two people have exactly identical DNA Except identical twins DNA Fingerprint: unique set of DNA fragments Used to determine paternity, solve crimes, etc. 99. 9% all human DNA is identical Focus on highly variable areas of tandem repeats Mutations occur within families and are more common in these areas

Gel electrophoresis: uses an electric current to force DNA fragments through a gel DNA is negative Size of fragment determines how far it migrates The fewer tandem repeats the farther it travels Differences in homologous DNA sequences resulting in fragments of different lengths are restriction fragment length polymorphisms (RFLP’s)

15. 4 DNA Sequencing 1995 – entire DNA sequence for a bacterium was determined 4/25/03 – Human genome completed Several bacteria, yeast, Drosophila, C. elegans worm, Arabidopsis weed, Mickey…a mouse, just completed 3/31/04 – a rat) Used a sequencing machine

15. 5 Isolating Genes Genomic Library: set of DNA fragments from an organism’s genome Complementary RNA sequence can be synthesized with a radioactive isotope tag called a probe Used to find a specific gene Tags the gene whenever encountered Gene may then be isolated

15. 6 Using the Technology True human insulin is now manufactured Also somatotropin (growth hormone), blood-clotting factors, hemoglobin, interferons (cancer research), and various other drugs and vaccines Bacteria for oil spill clean up and other environmental pollution

15. 7 Designer Plants Genetically engineered plants have been developed for pharmaceuticals, herbicide, pest, and disease resistance, larger and tastier plants, fruits, and vegetables with greater yields Corn, cotton, potato, soy bean, etc

15. 8 Gene Transfers in Animals Cloning holds promises for future Clone organs and tissues Possibly modify animals to be more disease resistant and produce greater quantities of products Not currently occurring in farm animals

1997 – the first animal was cloned – Dolly a lamb 1. Remove nucleus from cell 2. Transfer nuclei from desired cells into unfertilized eggs 3. Implant the “zygote” into surrogate mother Since Dolly – we have cloned mice, rats, cows, cats, mules, horses, and Rhesus monkeys along with a couple of endangered animals

Human Genome HGP – an int’l effort to map and sequence all human genes 15 countries started 11/1/90 and finished 4/25/03 (50 years after Watson & Crick paper published) 1. Genome – only 30, 000 genes so it took less time Includes mapping & sequencing of other species for comparison 2. RNA transcription – more difficult since 30, 000 genes code for 80, 000 proteins due to alternative splicing 3. Proteome – quest for every human protein

15. 9 Who Gets Enhanced? � HGP already has an ethics committee due to insistence of James Watson � HGP needs to be used to help people and must be regulated by laws � Must prevent invasion of privacy and discrimination by insurance companies, employers, etc. � Must prevent Eugenics: purging of “undesirable” traits from human population (Hitler) � Science provides society with knowledge and opportunities – society requires rules and constraints to prevent abuse

CHAPTER 15: GENETIC ENGINEERING Section 15 -3: Applications of Genetic Engineering

Agriculture and Industry � � Genetic engineering used to improve products we get from plants and animals Could lead to better, less expensive, more nutritious food, and safer manufacturing processes

GM Crops � � Genetically modified plants since 1996 Example: adding bacterial genes that produce Bt toxin - kills insects � No pesticides needed � Higher crop yields � � Resistance to herbicides, viral infections, rot and spoilage Some being made to produce plastics

GM Animals � 30% of milk produced by cows modified with hormones that increase milk production � Pigs that produce leaner meat , high levels of omega-3 � Salmon with extra growth hormone to make them grow quicker � Canada – goats that produce silk � Goat milk with antibacterial enzymes

GM Animals � � � Scientists hoping to clone transgenic animals to increase food supply and save endangered species 2008 – gov’t allowed sale of meat and milk from cloned animals Avoid complications of traditional breeding, duplicate exactly

Preventing Disease � � � Making more nutritious plants Producing antibodies to fight disease Make proteins we need

Medical Research � � � Transgenic animals used as test subjects Study defective genes, disease progression Conduct drug tests

Treating Disease � Recombinant DNA technology used to make human proteins to treat disease – human growth hormone, insulin, blood-clotting factor, cancer-fighting proteins � Also gene therapy – the process of changing a gene to treat a medical disease or disorder � Absent or faulty gene replaced with a normal, working gene

Treating Disease � � � Very risky Need a more reliable way to insert working genes Make sure it’s not harmful

Genetic Testing � Hundreds of diseases/disorders can be tested for � Some use labeled DNA probes that can detect disease-causing alleles � Some search for changes in cutting sequences � Some use PCR to detect differences in length between normal and abnormal alleles

Examining Active Genes � � Not every gene is active in ever cell all the time Understand how cells function by studying active genes using DNA microarray technology - measures level of activity of genes

DNA Microarray � � Glass slide or silicon chip to which spots of single-stranded DNA are attached – each spot with a different DNA fragment Colored tags label source of DNA

DNA Microarray Red spots = more cancer m. RNA Green spots = more normal m. RNA Yellow spots = both

Personal Identification No 2 individuals are genetically identical (except identical twins) Regions of chromosomes contain repeated sequences that do not code for proteins that differ from person to person

Personal Identification � � DNA fingerprinting analyzes sections of DNA that have little/no function but that vary widely from one individual to another Use REs to cut DNA into fragments, electrophoresis to separate fragments

Personal Identification � � � DNA probe detects fragments with highly variable regions If enough probe/enzyme combos are used, resulting banding pattern can be used to distinguish a person DNA from any tissue can be used

Forensic Science � � � Forensics = study of crime scene evidence Uses DNA fingerprinting to solve crimes, overturn convictions Wildlife conservation

Establishing Relationships � � � When genes are passed parent to child, the markers used in DNA fingerprinting are scrambled Y chromosome, however, passed directly from father to son with few changes – paternity tests Pieces of mitochondrial DNA (mt. DNA) also passed from mother to child directly – 2 people with the same mt. DNA share a common maternal ancestor