INTERNATIONAL TURKISH HOPE SCHOOL ACADEMIC YEAR CHITTAGONG SENIOR SECTION BIOLOGY HANDOUT SELECTIVE BREEDING, GM & CLONING CLASS 9 AND 10

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1 INTERNATIONAL TURKISH HOPE SCHOOL ACADEMIC YEAR CHITTAGONG SENIOR SECTION BIOLOGY HANDOUT SELECTIVE BREEDING, GM & CLONING CLASS 9 AND 10 Name :... Date:... Selective Breeding Selective breeding Choosing individuals for breeding based on their characteristics. Individuals with desired characteristics are bred together to produce offspring which express the desired characteristics from both parents. Selective breeding can also be carried out to combine particular combinations of characteristics. Selective breeding has produced many familiar vegetables and animals. The Brassica plant for example, has been selectively bred to form cabbage, cauliflower, broccoli and other things. Wolves have been selectively bred to give us dogs such as the sheepdog. 1 P a g e

2 Selective breeding can produce plants and animals with characteristics that in: Plants Give higher yields Are resistant to certain diseases Are resistant to certain pest damage Are hardier (they survive harsher climates) Have a better balance of nutrients e.g. plants that contain more of the types of amino acids needed by humans Animals Produce more meat, milk or eggs Produce more fur or better quality fur Produce more offspring Show increased resistance to diseases and parasites 2 P a g e

3 Genetic modification The removal of a gene from one organism and its insertion into the DNA of another organism so that the gene is expressed. This is sometimes called recombinant DNA technology and the DNA formed is called recombinant DNA. The organism containing the recombinant DNA is called the transgenic organism, or genetically modified organism (GMO). Vectors are bacterial plasmids or viruses that can insert genes into cells. Insulin Production 3 P a g e

4 1. The target gene is extracted (human insulin gene) from the donor cell using restriction enzymes. 2. Many copies of the insulin gene are made. 3. The bacterial DNA (plasmid) is cut open using restriction enzymes. These enzymes cut the DNA at certain sites of the genetic code. 4. The gene is inserted into the bacterial DNA using DNA ligase enzymes. These enzymes zip the gene into the DNA so that it becomes part of it. 5. The new plasmids are put back into bacterial cells which are then tested to see if they contain the recombinant DNA. Any bacteria that don t are discarded. 6. These bacteria can now produce human insulin. This takes place in an industrial fermenter to produce large quantities. Other chemicals produced in this way are growth hormone and bloodclotting factor. Genetic engineering in plants 4 P a g e

5 1. The required gene (e.g. the gene for toxin produced by bacteria that kills any caterpillars that eat them) is extracted from the source organism using restriction enzymes. 2. The gene is inserted into a bacterial plasmid using a ligase enzyme. 3. The plasmid is then inserted into a bacterium that normally infects plants. 4. The bacterium is made to infect plant cells. The recombinant DNA of the plasmid is carried into the nucleus of each plant cell and inserts the gene into the plant cell s DNA. 5. The plant cells are tested to make sure they contain the recombinant DNA. 6. Those plant cells containing the inserted gene are grown to produce whole new plants. 7. All the cells of the new plant have been produced by mitosis of the original transgenic plant cell so they all contain the inserted gene and all produce the new characteristic. In this example all the plant cells will produce the toxin that kills caterpillars when they eat the plant. Advantages of Modifying Plants: Increased resistance to a range of pests and pathogens Increased heat and drought tolerance Increased salt tolerance A better balance of nutrients Increases yield and food production to satisfy the growing demand. Increased frost resistance e.g. frost resistant strawberries Increased shelf life e.g. non squash tomatoes Easier to eat e.g. easy-peel oranges 5 Page

6 Disadvantages of Modifying Plants: Transgenic products may be harmful to some new proteins may cause allergies. The transgenes may spread uncontrollably into other closely related species which then have a genetic advantage over other plants unbalancing the food web. It may cause the emergence of pest, insect, or microbial resistance due to natural variation. A new gene may disrupt normal gene function and cause cancer. Cloning Cloning describes any procedure that produces genetically identical offspring. Usually the offspring has a desirable phenotype and may have been produced by selective breeding or genetic engineering. In plants; Micropropogation Note: These explants are being grown in vitro using nutrient media. In vitro means made in a laboratory or other controlled experimental environment rather than in a natural setting. 1. Explants (small pieces of plant) are cut from the growing tips of the chosen plant. 2. The explants are sterilised by washing them in mild bleach to kill any microorganisms. 6 P a g e

7 3. The explants are transferred onto a jelly-like growth medium that contains nutrients as well as plant hormones to encourage cell division. 4. When there are many cells they can be separated into smaller pieces and grown again. 5. Some explants are placed onto a growth medium with different concentrations of plant hormones to encourage them to grow roots, shoots and leaves. 6. When the tiny plants are big enough to be handled they are transferred to another growth medium and eventually to normal compost. The advantages to micropropagation are; Large numbers of genetically identical plants can be produced very rapidly. Species that are difficult to grow from seed or from cuttings can be propagated this way. Plants can be produced at any time of the year. Large numbers of plants can be stored easily. Genetic modifications can be introduced into thousands of plants quickly, after modifying only a few plants 7 Page

8 Q. Describe how micropropagation (tissue culture) can be used to produce large quantities of identical plants. (6) 1. First of all, Explant or Callus are taken by cutting small pieces of plant. 2. It is placed on Agar plate containing nitrates and hormones. 3. The plate or the environment has to be sterile. 4. The growth promoter or hormone helps in developing root from the callus. 5. The temperature, sunlight, carbon dioxide and moisture is maintained using a fogging greenhouse. 6. Many genetically identical clones are formed, which have the same DNA. 7. The process is quick and can be used all the year round. Q. The passage below describes stages involved in the process of micropropagation in plants. (9) Very small pieces are cut from the tips of stems or side shoots of a plant. When these pieces have been removed they are called explants. They are cut to a size of about 0.5 to 1 mm. They are then placed in agar/nutrient/gowth medium containing minerals/glucose and growth regulators/ vitamins, which help the pieces to grow into small plants. When the small plants have grown roots they are transferred to a glasshouse. They are grown in pots containing compost/soil and conditions such as temperature/light and carbon dioxide/humidity can be controlled. The small plants produced are called clones, which means they are genetically identical. 8 Page

9 In animals 1. A mature diploid cell was removed from the udder of an adult female sheep and the nucleus removed. The cell is discarded, the nucleus is kept. 2. An unfertilised egg cell was taken from another female sheep of a different breed. 3. The nucleus is removed from the unfertilised egg cell (the cell was enucleated) and discarded. 4. The diploid nucleus from the udder is inserted into the cytoplasm of the enucleated egg cell. 5. The cell is treated so it divides by mitosis. 6. The dividing cell forms an embryo and is implanted into the uterus of another female sheep. 7. The lamb has all the characteristics of the sheep from which the udder cell had been taken. Dolly the first cloned animal was produced in this way. This technique has the potential to produce transgenic organisms. If a gene from another organism is inserted into the DNA of the donor nucleus before it is placed in the enucleated cell, then all of the cells of the developing embryo will contain the recombinant DNA. 9 P a g e

10 There are several potential uses for cloned transgenic organisms; Research Animals created in this way could be better models for human disease. Transgenic mice can be produced with human disease traits. Research is made easier because mice grow and breed faster than larger animals. Drug production Transgenic animals can be used to produce human antibodies or other human proteins for use as medicinal drugs. Goats have been made to produce a blood anti- clotting chemical in their milk, which is separated and purified for people who are unable to produce it. Sheep can produce several human proteins to treat conditions such as emphysema and cystic fibrosis. Organ production Pigs can be genetically modified to produce organs, such as kidneys, suitable for human transplantation. This could help overcome the shortage of human donors. 10 Page