2 Selective Breeding Selective Breeding People select organisms with desired characteristics to produce next generationTakes advantage of naturally occurring variationSelective breeding of teosinte grass by native Americans 6000 years ago led to corn as we now know it
3 Selective Breeding Hybridization Cross dissimilar organisms to bring together best of both organismsEx: disease resistance + increased yieldBenefits include hardier plantsAmerican botanist Luther Burbank developed more than 800 varieties of plants using selective breeding methods.
4 Selective Breeding Inbreeding Breeding a line of organisms with similar characteristicsEx: dog breedsRisks- decreased genetic variation and increased susceptibility for certain diseases/disordersEx: hip dysplasia
5 Increasing VariationProcess used to increase the variation normally present in natureBut why?Biotechnology is the application of a technological process, invention, or method to living organisms.
6 Increasing variation Can be accomplished through mutations Mutations are usually random, but can be induced via radiation and chemical exposurePotential to yield few beneficial mutants with desirable characteristics not found in original population
7 Increasing VariationBacteria- can treat millions at a time increasing chances of producing useful mutantsEx: oil-digesting bacteria
8 Increasing VariationPlants-arresting chromosome separation during meiosis to produce polyploidsKnown to be more vigorous than diploid relatives
9 13-2 Manipulating DNA Mutations are random Having a way to alter DNA in a very specific way to achieve a particular result has huge advantagesScientists can now use the knowledge of DNA structure and its chemical properties to study and change DNA molecules
10 Tools of Molecular Biologists Genetic engineering allows biologists to rewrite the DNA code of an organismModern techniques employed canExtracting DNA from cellsCutting it into smaller piecesIdentifying sequences of bases in DNA (genes)Making unlimited copies
11 Finding Genes Started with Douglas Prasher (1987) Prasher wanted to find a specific gene in a jellyfish that codes for a molecule called green fluorescent protein, or GFPGFP is a natural protein that absorbs energy from light and makes parts of the jellyfish glowPrasher thought that GFP from the jellyfish could be linked to a protein when it was being made in a cellbit like attaching a light bulb to that molecule
12 Finding Genes (GFP specifically) Prasher compared part of the amino acid sequence of the GFP protein to a genetic code tablewas able to predict a probable mRNA base sequence that would code for this sequence of amino acidsThen used a complementary base sequence to “attract” an mRNA that matched his prediction and would bind to that sequence by base pairing.After screening a genetic “library” with thousands of different mRNA sequences from the jellyfish, he found one that bound perfectly
13 Finding GenesTo find the actual gene that produced GFP, Prasher took a gel in which restriction fragments from the jellyfish genome had been separated and found that one of the fragments bound tightly to the mRNAThat fragment contained the actual gene for GFPThis method is called Southern blotting, after its inventor, Edwin Southern.
15 Finding GenesToday it is often quicker and less expensive for scientists to search for genes in computer databases where the complete genomes of many organisms are available.
16 Copying DNA (specific genes) First step is a polymerase chain reaction (PCR)Heat a piece of DNAseparates its two strandsDNA cools and added primers bind to the single strandsDNA polymerase starts copying the region between the primersThese copies can serve as templates to make still more copies.
17 Polymerase Chain Reaction Once biologists find a gene, a technique known as polymerase chain reaction (PCR) allows them to make many copies of it.1. A piece of DNA is heated, which separates its two strands.
18 Polymerase Chain Reaction 2. At each end of the original piece of DNA, a biologist adds a short piece of DNA that complements a portion of the sequence.These short pieces are known as primers because they prepare, or prime, a place for DNA polymerase to start working.
19 Polymerase Chain Reaction 3. DNA polymerase copies the region between the primers. These copies then serve as templates to make more copies.4. In this way, just a few dozen cycles of replication can produce billions of copies of the DNA between the primers.
20 Copying DNAIt is relatively easy to extract DNA from cells and tissues.The extracted DNA can be cut into fragments of manageable size using restriction enzymes.These restriction fragments can then be separated according to size, using gel electrophoresis or another similar technique
22 Recombinant DNA Technology It is a form of genetic engineering that cleaves DNA into small fragments and inserts those fragments into a host organismHost may be the same or a different species
23 Transgenic OrganismsOrganisms who have incorporated foreign DNA in their chromosomes and use this new DNA as their own
24 How to Produce a Transgenic Organism Step 1: Isolate the gene in the foreign DNA that you want to insertEx: isolate the gene for beta carotene in a daffodil so you can then add it to rice
25 Step 2: Cut it out of the chromosome (in daffodil) using restriction enzymes. Restrictions enzymes are bacterial proteins that have the ability to cut both strands of the DNA molecule at a specific nucleotide sequenceResulting fragments can have blunt ends or sticky ends
26 Some Commonly used REs EcoRI (eco r one) HindIII (hindi three) BamHI (bam h one)TaqI (tack one)
27 Step 3: Cut host’s DNA with the same RE so cut ends will match up When DNA from two different organisms joins up- recombinant DNA is formed
28 Vectors Getting DNA from one organism into another requires a vector The vector introduces the new DNA into the host cellBacterial DNA is often used as a vector
29 Bacterial DNABacteria contains plasmids- small rings of DNA separate from the bacterium’s larger circular chromosomeThe foreign DNA is inserted into the plasmid by cleaving both using the same restriction enzymeSticky ends match up and foreign DNA becomes part of plasmid
30 Gene CloningPlasmid with foreign DNA (Now considered recombined DNA) is inserted into a bacterial cellPlasmids can replicate within the cell and can produce up to 500 copies in the cell
31 Soon Tons of Copies! Bacteria clones the recombinant DNA How? Clones-genetically identical copiesHow?Bacterial cells themselves will reproduce quickly, each with hundreds of copies of the recombinant DNA inside (plasmid + foreign DNA)
32 Introduction into Host Cell Plasmid is then inserted into a host’s chromosome where it will be replicated each time the cell replicates along with the organism’s other chromosomesThe host cell can transcribe/translate that recombinant DNA into protein just like all other proteins coded in its DNA