Genetic Engineering

Selective Breeding Choosing animals/organisms with desired characteristics to breed and produce offspring Goal: to pass desired traits to next generation of organisms Examples: Dogs, Cats, Farm animals and Crop plants

Selective Breeding Hybridization- Crossing dissimilar individuals to bring together the BEST traits of BOTH organisms HOPEFULLY, offspring of cross are HARDIER than either parent Example: in Crop plants combine disease resistant of one with food-producing capacity of another

Selective Breeding Inbreeding- Continued breeding of individuals with similar characteristics Seeking to maintain desired characteristics of organism are maintained over many generations Risk- Since members of breed genetically similar; may increase chances of recessive disease being expressed First Cousins NOT ALLOWED to marry!

Selective Breeding Increasing variation- breeders do so by DELIBERATELY inducing mutations (ultimate source of genetic variability) Using mutagens to increase variability! Examples: new bacterial strains (clean up oil-WOW) or new kinds of flowers Polyploidy- accepted in plants; more than two chromosomal sets

DNA Manipulation Until very recently, plant and animal breeders were unable to modify the genetic code of organisms Forced to work with inherent variation in nature Even with addition of variation via mutations, changes in DNA produced were random and unpredictable

DNA Manipulation TODAY, scientists can use their knowledge of DNA structure and its chemical properties to alter the sequence of DNA Techniques include: DNA extraction, cut DNA into smaller pieces, identify DNA sequence one base at a time as well as make unlimited copies of DNA

Genetic Engineering Genetic Engineering- making changes in the DNA code of a living organism 1. DNA extraction- cells are opened and DNA is separated from other cell parts 2. Restriction enzymes- proteins that preferentially cut DNA at a specific nucleotide sequence 3. Gel electrophoresis- Load DNA onto an end of a porous gel and apply an electric charge, separating DNA fragments based on size

Recombinant DNA Combining DNA from different organisms/different sources Using SAME restriction enzyme (cut and paste), take a gene from one organism and attach it to the DNA of another organism

Cell Transformation Transformation- A cell takes in DNA from outside the cell. This external DNA becomes part of the cell’s DNA Plasmid- Foreign/transforming DNA added to a small, circular DNA molecule

Cell Transformation 2 essential features: 1. Plasmid has DNA sequence serving as an origin of replication; if plasmid gets inside bacterial cell, sequence ensures plasmid that it will be replicated 2. Contains genetic marker- allows one to distinguish bacteria containing/transformed by plasmid vs. those that have not-Antibiotic resistence gene

Transforming Plant cells

Gel electrophoresis After restriction digestion, a mixture of DNA fragments (different sizes) is loaded onto one end of a gelatin material An electric voltage is applied to the gel DNA molecules (negatively charged-WHY?) move toward the positive end of gel

Gel electrophoresis The smaller the DNA fragment, the faster (and further on the gel) it moves Gel electrophoresis used to: compare DNA sequences of different organisms or different individuals within species Locate and identify one particular gene out of millions of genes in individual’s genome

Using DNA sequence Knowing organism’s DNA sequence, one can do the following: 1. Study specific genes 2. Compare genes to other organisms genes 3. Identify functions of different genes and gene combinations

Reading DNA sequence Small, single stranded DNA pieces placed in test tube with DNA polymerase A supply of all four “free” nucleotide bases is then added, along with one “labeled” base (label with fluorescent dye) When DNA polymerase adds labeled base, replication is terminated

Reading DNA sequence When using all 4 “labeled” bases-each with different fluorescent color-a series of tiny DNA fragments is created Separate fragments via gel electrophoresis Pattern of colored bands tells exact sequence of bases in the DNA

Polymerase Chain Reaction PCR- Making multiple copies of a specific gene of interest; a photocopy machine stuck on “print.” 1. At each end of DNA “gene of interest” is placed a COMPLEMENTARY DNA sequence (known as a “primer” priming DNA replication; Start point of DNA polymerase! 2. DNA heated to high temperature to separate two template strands

Polymerase Chain Reaction 3. Next, DNA solution is cooled, allowing primers to ANNEAL to template strands (single stranded DNA) 4. DNA polymerase starts making copies of region between primers 5. NOW, primers themselves can then serve as templates to AMPLIFY “gene of interest” that lies between primer sequences