Genetic Engineering

Genetic Engineering Chapter 13

Changing the Living World 13-1

Selective Breeding • Selective breeding – (artificial selection) • Breeders select individuals with desirable traits to breed. • Offspring inherit desirable traits from parents (hopefully).

Selective Breeding Luther Burbank used selective breeding to develop Shasta daisies, a popular variety.

Selective Breeding • Hybridization • Crossing dissimilar individuals to produce offspring with “hybrid vigor”.

Hybridization A mule is a cross between a horse and a donkey.

Selective Breeding • Inbreeding • Crossing similar individuals to maintain desired traits.

Inbreeding Inbreeding maintains the desirable traits of Labradors, but may make the breed more susceptible to disease and physical abnormalities.

Hybridization Inbreeding Dissimilar organisms Similar organisms Organism breed B Organism breed A Organism breed A Retains desired characteristics Combines desired characteristics Concept Map Section 13-1 Selective Breeding consists of which crosses which crosses for example for example which which

Increasing Variation • Inducing mutations increases variation in a population. • Variation in a population is a good thing. • Radiation and chemicals are used.

Inducing Mutations Bacteria have been induced to digest oil.

Induced mutations Strawberries have been induced to be polyploid making bigger, sweeter strawberries.

Manipulating DNA 13-2

Genetic Engineering • Making changes in the genetic code.

Tools of Molecular Biology DNA Extraction lyses the cells (detergent), then separates the DNA from protein histones using a protease enzyme. Lastly the DNA is precipitated.

Tools of Molecular Biology Restriction Enzymes cut DNA into fragments at certain base sequences. Restriction enzymes only cut their specific sequence.

Restriction Enzymes Recognition sequences DNA sequence

Restriction Enzymes Section 13-2 Recognition sequences DNA sequence Restriction enzyme EcoRI cuts the DNA into fragments. Sticky end

Tools of Molecular Biology Gel Electrophoresis Separates DNA fragments based on size. An electric current pulls the fragments across a gel and produces a unique “fingerprint”. Used in forensics

Figure 13-6 Gel Electrophoresis Power source DNA plus restriction enzyme Longer fragments Shorter fragments Gel Mixture of DNA fragments

Using the DNA Sequence In DNA Sequencing DNA polymerase and fluorescent labeled nucleotides determine the order of bases in a fragment.

Figure 13-7 DNA Sequencing

Using the DNA Sequence In gene splicing DNA is cut into fragments and pasted together to create recombinant DNA

Using the DNA Sequence Polymerase Chain Reaction (PCR) makes unlimited copies of a gene.

Figure 13-8 PCR DNA polymerase adds complementary strand DNA heated to separate strands DNA fragment to be copied PCRcycles 1 DNAcopies 1 3 4 4 8 5 etc. 16 etc. 2 2

Cell Transformation 13-3

Cell Transformation • When a bacterial cell takes in DNA from outside the cell, the external DNA gets incorporated into the bacterium’s own DNA. • Recombinant DNA has been made. • The cell has been transformed. It will make a new protein(s).

Transforming bacteria • Bacterial plasmids (circular DNA) are used to produce human hormones (HGH, insulin, clotting factor). • Plasmids are useful because they are readily taken in by bacteria and they easily replicate within a cell. • Also genetic markers in the plasmid help isolate transformed cells from non-transformed cells. • Typically the gene for resistance to antibiotics is used as a genetic marker. After transformation, the culture is treated with an antibiotic to kill all non-transformed cells.

Figure 13-9 Making Recombinant DNA Section 13-3 Gene for human growth hormone Recombinant DNA Gene for human growth hormone DNA recombination Human Cell Sticky ends DNA insertion Bacterial Cell Bacterial chromosome Bacterial cell for containing gene for human growth hormone Plasmid

Transforming plant cells • Plant cells don’t readily take in external DNA. • Plant cells are grown in culture with their cells walls removed. • Then plasmids are directly injected into the cells or carried into the cells with a bacterium.

Figure 13-10 Plant Cell Transformation Section 13-3 Agrobacterium tumefaciens Gene to be transferred Cellular DNA Inside plant cell, Agrobacterium inserts part of its DNA into host cell chromosome Recombinant plasmid Plant cell colonies Transformed bacteria introduce plasmids into plant cells Complete plant is generated from transformed cell

Transforming animal cells • DNA is injected directly into egg cells. • DNA can be carried into cells with viruses. • Once inside the nucleus, recombinant DNA can replace a host cell gene making it possible to treat disorders caused by single genes. • This therapy is called “gene replacement”. • Ex: cystic fibrosis

Knockout Genes Section 13-3 Recombinant DNA Flanking sequences match host Host Cell DNA Target gene Recombinant DNA replaces target gene Modified Host Cell DNA

Applications of Genetic Engineering 13-4

Transgenic Organisms • Transgenic organisms contain genes from different species. • Transgenic bacteria produce human proteins. • Transgenic animals grow faster and produce leaner meat. • Transgenic plants are more resistant to disease. • Foods obtained from transgenic organisms are labeled “genetically modified”.

Cloning A clone is a member of a genetically identical population. In 1997 the first mammal was cloned, a sheep named Dolly.

Figure 13-13 Cloning of the First Mammal Section 13-4 A donor cell is taken from a sheep’s udder. Donor Nucleus These two cells are fused using an electric shock. Fused Cell Egg Cell The nucleus of the egg cell is removed. An egg cell is taken from an adult female sheep. The fused cell begins dividing normally. Embryo Cloned Lamb The embryo is placed in the uterus of a foster mother. The embryo develops normally into a lamb—Dolly Foster Mother

Genetic Engineering