Genetic Engineering Chapter 13 Genetic engineering Making changes

Genetic Engineering Chapter 13

Genetic engineering • Making changes to the DNA code of an organism – Selective breeding – Increased variation – Cloning – Genetically modified foods

Changing the Living World • Crop Selection – Grower selects the seeds of the best crops to plant each year – Eventually alleles are uniform in producing desirable traits (REMEMBER: GENETICS!) • Selective breeding: allowing only animals (or plants) with desired characteristics produce the next generation • Domestic animals and crops are made by selective breeding

Species vs. breed Species • A group of organisms that are able to reproduce together and in doing so create viable offspring

Species vs. Breed • animals or plants within a species having a distinctive appearance and typically having been developed by deliberate selection

Selective Breeding • Different breeds are not different species

Types of selective breeding Hybridization • Crossing dissimilar individuals to bring together the best of both organisms – Offspring are “better” then either parent Inbreeding • Continued breeding of individuals with the same characteristics • Used to maintain a desired characteristic • Risk bringing together 2 recessive traits that cause a defect

Hybridization vs. Inbreeding 1. Pick a crop or animal breed 2. Pick 2 desirable characteristics 3. How does hybridization allow for the production of the “best” offspring 4. How does inbreeding allow the “best” traits to stay in the offspring.

Cont. • Challenges with Hybridization: – Takes many years to bring a new variety of crop to market. – Linkage between genes require trade-offs that can compromise the crop • video

Genetic Engineering • Making changes to the DNA code – DNA extraction • How did we do this? ? ? – Cutting DNA • Restriction enzymes- cut the DNA at a specific sequence of nucleotides

Genetic Engineering • Separating DNA – Gel Electrophoresis

Manipulating DNA • How are scientists able to change DNA? • Based on the knowledge of DNA structure, scientists are able to change DNA molecules.

Cutting and Pasting • Short sequences of DNA are added to the original DNA strand

Making Copies • Polymerase chain reaction (PCR) – Primers are added to either end of the DNA strand – DNA polymerase is added and starts making copies of the DNA

Cell transformation • Cell Transformation: genetic alteration of a cell resulting from the uptake of foreign DNA – Outside DNA becomes apart of the cell DNA – Produces recombinant DNA

Steps the Cell Transformation 1. DNA is joined to a small bacterial plasmid (DNA)

Step 1 • Restriction enzymes – Cuts DNA at a specific sequence – Must match the DNA sequence exactly

Why are plasmids used? • Contains a DNA sequence that promotes replication • Contains a genetic marker that makes it easy to find – A gene that is used to find the plasmid in a cell

Cell Transformation 2. DNA is injected into plant or animal cells 3. When plant grows the DNA is incorporated into every cell Animation

Cell transformation Animation

Genetic variation • Genetic variation: different forms of the same gene (alleles) • Why is variation important in organisms? • Why would plant and animal breeders want there to be variation among individuals in a species?

Increasing Variation • What causes variation among species? – Genetic variation can be increased in a population by introducing mutations – Mutations are the source of variation • Mutation rate is increased by using radiation and chemicals – Plant and animal breeders induce mutations by exposing individual organisms to radiation and chemicals

A new way to induce variation • Why would breeder/ scientist look for a new way to induce variation? – Cant control the type of mutation – Many mutations are harmful – Organisms can be killed during exposure to radiation and chemicals • Genetic Engineering allows scientist to choose exactly how they are changing the organism

Steps to Genetically modifying a crop • Genes are transferred through bacterial plasmids 1. 2. 3. 4. 5. 6. Isolation of the gene(s) of interest Insertion of the gene(s) into a transfer vector Plant transformation Selection of the modified plant cells Regeneration into whole plants via tissue culture Verification of transformation and characterization of the inserted DNA fragment 7. Testing of plant performance 8. Safety assessment

Reading the sequence 1. A single stranded DNA is placed in a test tube 2. DNA polymerase and nucleotides are added to the test tube – Some nucleotides have chemical dyes attached to the that serve as genetic markers 3. When a dye labeled base is added synthesis is terminated 4. Segments are put together in order of length Diagram pg. 324

Using the DNA sequence • DNA can be read, studied and even changed How DNA can be used • Study specific genes • Compare genes of one organism to genes of another • Discover the function of different genes and gene combinations

How is DNA read • Gel Electrophoresis- DNA is separated based on charge and size

Forensics

How is DNA read • Genetic Markersnucleotides that have a specific dye attached to them • When the DNA is ran through a gel the nucleotides appear a specific color

Applications of Genetic Engineering

Transgenic Organisms • Transgenic organisms- contain genes from other species – How is this possible?

Transgenic Microorganisms • First transgenic organisms to be produced • Reproduce quickly and easily • Help to treat human disorders at lower cost and safer Examples of use • Protein production (insulin, clotting factor)

Transgenic Animals • Used to study genes and improve food supply Example: 1. Mice that have immune systems similar to humans (used to test disease/drugs) 2. Livestock with extra copies of growth hormone (produce leaner meat and more milk)

Transgenic Plants • Used to improve food supply – Produce natural insecticides – Resist weed killing chemicals Example: Genetically modified food supply – 52% of soy beans – 25% of corn – Rice

GM foods Benefit Risk • Reduced pesticides and herbicide use • Reduced Fertilizer use • Use of land recovery • Development of specialty crops • Allergies • Gene Flow • Damage to animals from pollen • Transfer of Antibiotic resistance • Alteration of soil ecology • Dangers of eating foreign DNA

Cloning • The process of producing populations of genetically identical individuals – The copied material, which has the same genetic makeup as the original, is referred to as a clone.

Gene cloning • gene cloning – Copies of genes • Using recombinant DNA to create multiple copies of the same gene

Reproductive cloning • reproductive cloning – Copies of whole organisms • Cloning is the creation of an organism that is an exact genetic copy of another. – Identical twins are natural clones • Somatic cell nuclear transfer – researchers isolated a somatic cell from an adult female. Next, they transferred the nucleus from that cell to an egg cell from which the nucleus had been removed.

Cloning

Therapeutic Cloning • therapeutic cloning – Produces embryonic stem cells for research • Stem cells are used to study human development and diseases – Stem cellsundifferentiated cells

Human Cloning • Would a human clone be identical to the person it was cloned from? – Genetically? – Personality? – Opinions?

Ethics of Cloning • How could cloning be used to help us? • Why would some people not want cloning to be allowed? • Are there any cases where cloning would be accepted?

Genetically Modified foods • What is the science involved in genetic engineering crops? • How is genetic engineering different from more traditional genetic manipulations, such as hybridization? • What steps are usually involved in genetically modifying foods? • What are the known or projected risks and benefits of genetically modifying crops?