13-1 Changing the Living World

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1 13-1 Changing the Living World In the past, variation was limited to the variations already in nature or random variations that resulted from mutations. Now, scientists can change DNA and swap genes from one organism to another, designing new living things.

2 Selective Breeding Only breed those carrying the desired traits ex: dog breeders

3 Selective Breeding Two types: 1) Hybridization = cross organisms with different traits zorse spider goat

4 Selective Breeding Two types: 2) Inbreeding = breed organisms with similar traits

5 Selective Breeding Two types: 2) Inbreeding = breed organisms with similar traits Benefits: retain the unique traits of a breed Risks: increase the chance of inheriting two recessive alleles causing genetic defect

6 Increasing Variations Mutations are the ultimate source of genetic variations. Breeders can increase genetic variation by inducing mutations.

7 13 2 Manipulating DNA Genetic engineering is making changes to DNA The steps include: Extracting DNA (removal) Cutting DNA Separating DNA Making copies of DNA

8 Using a simple chemical procedure, cells are opened and DNA is separated and removed from the other cell parts. Extracting DNA

9 Cutting DNA DNA is too large to be analyzed, so it is precisely cut into smaller fragments using restriction enzymes

10 Cutting DNA Each restriction enzyme cuts DNA at a specific sequence of nucleotides

11 Cutting DNA The cut ends are called sticky ends because they may stick to complementary base sequences by means of hydrogen bonds.

12 Separating DNA DNA fragments are separated and analyzed using gel electrophoresis.

13 Gel electrophoresis: 1) DNA is cut and added to the gel.

14 2) An electric voltage is added and the DNA moves to the positive side. The smaller the piece of DNA, the faster and farther it moves.

15 3) The DNA makes a pattern of bands. This pattern can be compared to other DNA samples. Gel electrophoresis can be used to : - Locate and identify one particular gene out of tens of thousands of genes - Compare DNA to solve a crime

16 Making copies of DNA Scientists need many copies of a gene to study it, so they use polymerase chain reaction (PCR):

17 Making copies of DNA Three steps: 1) Separating: the double stranded DNA is heated and separated into single strands. DNA strands primer 1 polymerase primer 2 nucleotides

18 Making copies of DNA 2) Binding: primers (short segments of DNA acting as the starting point for new strands) bind to the DNA strands. DNA strands primer 1 polymerase primer 2 nucleotides

19 Making copies of DNA 3) Copying: DNA polymerase bind nucleotides to the original strands of DNA by complementary base pairing. DNA strands primer 1 polymerase primer 2 nucleotides

20 13 3 Cell Transformation Genetic engineering is the changing of an organism s DNA to give the organism new traits.

21 Genetic Engineering Genetic engineering is based on the use of recombinant DNA technology. Recombinant DNA = DNA that contains genes from more than one organism. Bacteria are commonly used for their plasmids in recombinant DNA.

22 Recombinant DNA Plasmid = tiny circular bacterial DNA Foreign DNA can be inserted into plasmids to make recombinant DNA.

23 Recombinant DNA Making recombinant DNA: 1) Both the plasmid and the foreign DNA are cut with the same restriction enzyme. 2) The sticky ends of the plasmid and the foreign gene match and bond together to form recombinant DNA.

24 Transformation A cell can be transformed using recombinant DNA. Transformation = A recombinant DNA is put inside a host cell and becomes part of the host DNA. Transformation results in transgenic organisms = organisms that contain genes from another organism

25 Transformation Recombinant DNA Gene for human growth hormone Gene for human growth hormone Human Cell Bacteria cell Cut by restriction enzyme producing sticky ends Bacterial chromosome Transformation Plasmid Bacterial cell containing gene for human growth hormone

26 Transforming Plant Cells In nature, there s a bacteria that can insert plasmid into plant cells, producing tumors. Scientists use this same bacteria, but insert foreign DNA, producing a recombinant plasmid that can infect plants. OR, DNA can be injected into some cells. OR, scientists can remove the cell wall and allow plant cells to take up the DNA on their own

27 Transforming Plant Cells Agrobacterium tumefaciens Inside plant cell, Agrobacterium inserts part of its DNA into host cell chromosome. Gene to be transferred Recombinant plasmid Cellular DNA Plant cell colonies Transformed bacteria introduce plasmids into plant cells. Complete plant generated from transformed cell.

28 Transforming Animal Cells DNA can be injected into egg cells Enzymes in the cell will insert the foreign DNA into the chromosomes of that cell.

29 Transforming Animal Cells Transgenic technology Nuclear transfer technology Embryos Transgenic animal Animal cloning Embryonic Stem cells

30 Recombinant DNA (combining DNA from one organism with DNA from Human gene another) Plasmid (bacterial DNA) Transformation (process of putting the recombinant DNA into the organism)

31 Transgenic Microorganisms Transgenic bacteria produce many important substances for health industry, because they reproduce quickly and are easy to grow. ex: Human proteins including insulin human growth hormone clotting factor

32 Transgenic Plants Much of our food supply, especially beans and corn, is transgenic or genetically modified (GM). Many crop grown GM plants now contain genes that produce a natural insecticide or resistance to chemicals or diseases.

33 Transgenic Plants Examples of GM plants: rice plant with added vitamin A seedless watermelon

34 Transgenic Animals Used to study genes and improve food supplies, for example: Mice with immune systems similar to humans are used to study how diseases may affect humans. Livestock with extra growth hormone genes grow faster and produce leaner meat

35 Stem Cells Stem cells are derived from human embryos before the cells differentiate. The embryonic stem cells can combine with nuclei of differentiated tissue needed. A new tissue can be cultured and used to heal a person by replacing damaged tissue.

36 Future Stem Cells? Future stem cells could be used in treating: Parkinson s Disease Alzheimer s Disease Diabetes Spinal Cord injuries

37 Cloning Clone = member of a population of genetically identical cells produced from a single cell Sheep, cows, pig, mice and other mammals have been cloned. Dolly was the first mammal cloned.

38 Cloning Dolly Cloning Donor nucleus Egg cell Fused cell Embryo Cloned lamb Foster mother