Ch 13 – Genetic Engineering 1

Selective Breeding Choose organisms with the desired traits and breed them, so the next generation also has those traits Nearly all domesticated animals and crops Luther Burbank ( ) developed >800 diff varieties of plants in his lifetime

Hybridization Breed two dissimilar organisms In plants – often results in better lines – hybrids are larger, stronger, etc In animals – hybrids produced may be weaker and sterile Ex – wolf x dog ---- weak wolf-dog Ex – horse x donkey ---- mule (sterile)

Horse x Donkey = Mule Lion x Tiger = Liger

Inbreeding Breeding two organisms that are very similar to produce offspring with the desired traits. Ex – dog breeds Risks – might bring together two individuals that carry bad recessive genes – many purebred dogs have genetic disorders that mutts don’t get.

Increasing Variation Induce mutations – the ultimate source of genetic variations among a group of organisms Mutagens used – radiation and chemicals Some organisms are formed that have more desirable variations.

GMO’s (Genetically modified organisms) + A strawberry resistant to frost = Arctic fish DNA strawberry

Producing new kinds of bacteria Can expose millions of bacteria at one time to radiation – increases chances of producing a successful mutant. Ex – bacteria that can digest oil have been produced this way

Producing new kinds of plants: Drugs that prevent chromosomal separation in meiosis have been used to create plants that have more than two sets of chromosomes (2n). These are called polyploid plants. Ex – bananas, citrus fruit, strawberries, many ornamental flowers Diploid corn Tetraploid corn

Manipulating DNA – tools of the molecular biologist DNA extraction – open the cells and separate DNA from all the other cell parts. Remember the pea lab?

DNA Extraction Chemical treatments Chemical treatments cause cells and nuclei to burst sticky The DNA is inherently sticky, and can be pulled out of the mixture “spooling” This is called “spooling” DNA 11

“Spooled” DNA 12

Cutting DNA Restriction enzymes Restriction enzymes cut DNA at specific sequences manageable fragments Useful to divide DNA into manageable fragments 13

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Electrophoresis size and charge DNA can be separated based on size and charge phosphate groups negatively The phosphate groups are negatively charged gelelectricity DNA is placed in a gel and electricity is run through 15

Electrophoresis Negative DNA Negative DNA moves toward the positive end Smallerfarther and faster Smaller fragments move farther and faster 16

Electrophoresis 17

Click here for animation about gel electrophoresis

Steps in DNA Sequencing Many copies of a single strand of DNA are placed in a test tube Many copies of a single strand of DNA are placed in a test tube DNA polymerase is added DNA polymerase is added A mixture of nucleotides is added some of which have dye molecules attached A mixture of nucleotides is added some of which have dye molecules attached Each base (A,T,C,G) has a different color dye Each base (A,T,C,G) has a different color dye 19

Steps in DNA Sequencing some dyed nucleotidessome regular ones By chance, some dyed nucleotides & some regular ones are added stop the chain Dye molecules are large and stop the chain from growing 20

DNA Sequencing multiple sizes with colors that can be identified The result is DNA fragments of multiple sizes with colors that can be identified 21

DNA Sequencing After the gel separates the resulting fragments by size, we 'read' the sequence from bottom to top. After the gel separates the resulting fragments by size, we 'read' the sequence from bottom to top. 22

Copying DNA Polymerase Chain Reaction Polymerase Chain Reaction Also called PCR A method of making many copies of a piece of DNA 23

Steps in Copying DNA A DNA molecule is placed in a small test tube DNA polymeraseDNA polymerase that can work at high temps is added 24

Steps in Copying DNA DNA is heated The DNA is heated to separate the two strands Primers Primers, short pieces of DNA complementary to the ends of the molecule to be copied, are added 25

Copying DNA DNA polymerase adds new bases to the separated strandsThe tube is cooled, and DNA polymerase adds new bases to the separated strands 26

PCR 27 Large amounts of DNA can be made from a small starting sample

Cloning Clone Clone- a member of a group of genetically identical cells asexual reproduction May be produced by asexual reproduction (mitosis) 28

Cloning organisms body cell egg cell A body cell from one organism and an egg cell from another are fused divides like a normal embryo The resulting cell divides like a normal embryo 29

Cloning “Dolly” 30

Cell Transformation A cell takes in DNA from outside the cell and that DNA then becomes part of the cell’s DNA. Bacteria – place DNA in the solution that bacteria live in, and some of that DNA will be taken in by the bacteria cells.

Bacteria Transformation using Recombinant DNA Cut a gene with a restriction enzyme out of a human cell (ex – gene for insulin or growth hormone work well) Cut a bacterial plasmid using the same restriction enzyme (DNA ends will be complementary) Insert Human gene into bacterial plasmid Insert plasmid back into bacterial cell Bacteria will multiply, and all offspring will have that gene – these bacteria will then follow the directions of the human gene and make the protein coded for (insulin or human growth hormone)

Bacterial plasmids in gene cloning 33

Applications of Genetic Engineering Gene for luciferase was isolated from fireflies and inserted into tobacco plants – they glowed! Transgenic organisms – contain genes from other species A transgenic mouse, which carries a jellyfish gene, glows green under fluorescent light.

35 Tobacco Plant containing Luciferin gene from Firefly

Transgenic Organisms Bacteria - Make human proteins like insulin Plants – 52% of soybeans, 25% of corn in US in year Some produce natural insecticide, some resist weed-killers, may soon be used to produce human antibodies; rice with vitamin A.