Chapter 15: Genetic Engineering

1. Chapter 15: Genetic Engineering Section 15-2: Recombinant DNA

2. Copying DNA • Breeders relied on natural variation produced by unpredictable mutations • Genetic engineers today can transfer genes from one organism to another, creating new living things • Need to isolate DNA, cut it with REs, separate it with gel electrophoresis

4. Finding Genes • If a scientists is looking for a particular gene, they can use a technique called Southern blotting analysis • Example: • In 1987 Douglas Prasher was looking for the gene in jellyfish that creates GFP, green fluorescent protein • Wanted to isolate and use this gene as a marker

5. Finding Genes • Figured out the most likely mRNA sequence for part of the amino acid sequence • Compared to thousands of others until he found the exact sequence in the jellyfish • Found the actual gene by taking a gel with jellyfish DNA that had been cut with REs • Found fragment that bound exactly to mRNA – this was the gene

7. Polymerase Chain Reaction • Technique used to make multiple copies of a gene once it is found • DNA heated to separate strands • Cooled, primers added • DNA polymerase produces complementary strands • Repeated over and over

10. Changing DNA • Scientists can create custom DNA molecules and insert them into living cells • Machines called DNA synthesizers produce short segments of DNA which can then be joined to natural sequences using DNA ligase or other enzyme for splicing

11. Combining DNA Fragments • If two DNA sequences from two different organisms are cut with the same RE, their sticky ends can be matched and they can be permanently bonded • Resulting molecules called recombinant DNA (recombinant DNA technology)

12. Plasmids and Genetic Markers • Sometimes genes were “lost” once they were inserted because they did not replicate along with the cell’s regular DNA • Now add the genes plus a replication “start” signal • Technique often used to create recombinant plasmids in bacteria (extra, circular DNA), yeasts • Use markers to identify inserted genes

14. Transgenic Organisms • Organisms that contain genes from other species • Produced by inserting recombinant DNA into genome of host organism • Contain genetic markers

15. Transgenic Plants • Plant cells often transformed with Argobacterium, which in nature inserts a gene into plants that produces tumors • Scientists deactivate the tumor gene, replace it with recombinant DNA, which then transforms plant cells

17. Transgenic Plants • Can also be produced by removing cell wall and allowing plant cell to pick up extra DNA, or inject DNA directly

18. Transgenic Animals • If the egg cell is large enough, DNA can be injected directly into nucleus and hopefully inserted into chromosomes • Now we can also eliminate genes by inserting new recombinant DNA within them

19. Cloning • A clone is a member of a genetically identical cells produced from a single cell • Uses a single cell from an adult organism to grow an entirely new organism – genetically identical • Animal cloning involves nuclear transplantation

20. Animal Cloning • Nucleus of unfertilized egg removed • Egg cell fused with donor nucleus taken from adult • Resulting diploid cell develops into embryo • Embryo implanted into uterine wall of foster mother • Develops until birth