Biology Module 6.4 - Cloning and Biotechnology

• What are clones?

  Genetically identical copies.

  
  

  The term can apply to cells or whole organisms.
• How are clones produced?

  By asexual reproduction in which the nucleus is divided by mitosis.

  
  

  Mitosis creates two identical copies of DNA, which are then separated into two genetically identical nuclei before the cell divides to form two genetically identical cells.

  
  

  These cells may not be physiclly or chemically identical as, after division, they may differentiateto form two different types of cell.
• What are the advantages of natural clones? (Clones formed in nature)?

  If the conditions for growth are good for the parent, then they will also be good for the offspring.

  
  

  Cloning is relatively rapid - population can increase quickly to take advantage of the suitable environmental conditions.

  
  

  Reproduction can be carried out even if there is only one parent and sexual reproduction is not possible.
• What are the disadvantages of natural clones?

  The offspring may become overcrowded.

  
  

  There will be no genetic diversity (except by mutation).

  
  

  The population shows little variation.

  
  

  Selection is not possible.

  
  

  If the environment changes to be less advantageous, the whole population is susceptible.
• What is vegetative propagation?

  The process of reproduction through vegetative parts of the plant, rather than through specialised reproductive structures.
• What are the methods plants use to reproduce?

  Runners, stolens, rhizomes and suckers

  
  

  Bulbs

  
  

  Corms

  
  

  Leaves

  
  

  Tubers
• What are runners, stolens, rhizomes and suckers?

  Many plants grow horizontal stems that can form roots at certain points. These stems are called runners or stolens if they grow on the surface of the ground, and rhizomes if they are underground.

  
  

  Some rhizomes are adapted as thickened over-wntering organs from which one or more new stems will grow in the spring.

  
  

  Suckers are new stems that grow from the roots of a plant - these may be close to the base of an older stem or could be some distance away. In all cases, the original horizontal branch may die, leaving the new stem as a separate individual.
• What are bulbs?

  An over-wintering mechanism for many perennial monocotyledonous plants.

  
  

  Consist of an underground stem from which grow a series of fleshy leaf bases

  
  

  There is often an apical bud, which will grow into a new plant in the spring.

  
  

  Often a bulb contains more than one apical bud and each will grow into a new plant.
• What are corms?

  Solid rather than fleshy like a bulb.

  
  

  An underground stem with scaly leaves and buds.

  
  

  Remain in the ground over winter. In the spring the buds grow to produce one or more new plants.
• What are leaves?

  Clones grow on the leaf margins .

  
  

  The immature plants drop off the leaf and take root.
• What are tubers?

  Another type of underground stem.

  
  

  Potatoes are tubers. One potato will grow into one or more plants.

  
  

  Each new plant can then produce many new tubers later that year.
• What are the examples of natural cloning in animals?

  Identical twins - occurs when a fertilised egg divides as normal, but the two daughter cells then split to become two separate cells. Each cell grows and develops into a new individual.

  
  

  The water flea and greenfly are examples of animals that commonly reproduce asexually to produce clones.
• How can horticulturists (plant growers) exploit a plant's natural ability to produce clones?

  By manipulating the way in which a plant grows, they can induce vegetative propagation, so they can get natural clones of the parent plant.

  
  

  Methods:

  
  

  Cuttings.

  
  

  Grafting - joining the shoot of one plant to the growing stem and root of another plant.

  
  

  Layering - bending a stem of a growing plant downwards so it enters the soil and grows into a new plant.
• How can you produce clones from cuttings?

  1. Use a scalpel to take a cutting from the end of a stem of your parent plant

  
  

  2. Remove the leaves from the lower end of your cutting, leaving just one at the tip.

  
  

  3. Dip the lower end of the cutting in rooting powder, which contains hormones that induce root formation.

  
  

  4. Then plant your cutting in a pot containing a suitable growth medium.

  
  

  5. Provide your cutting with a warm and moist environment by either covering the whole pot with a plastic bag or by putting it in a propagator.

  
  

  6. When your cutting has formed its own rootsand is strong enough, you can plant it elsewhere to continue growing.

  
  

  You can also take cuttings from other parts of a plant, such as a root or leaf.
• How can you produce clones from tissue culture?

  1. Cells are taken from the original plant that's going to be cloned. Cells from the stem and root tips are used because they're stem cells and they can develop into any type of cell.

  
  

  2. The cells are sterilised to kill any microorganisms - bacteria and fungi compete for nutrients with the plant cells, slowing growth rate.

  
  

  3. The cells are placed on a culture medium containing organic nutrients and a high concentration of plant hormones. This is carried out under aseptic conditions. The cells divide to produce a mass of undifferentiated cells. The mass can be subdivided to produce lots of plants very quickly.

  
  

  4. When the cells have divided and grown into a small plant they're taken out of the medium and planted in soil.
• What are the uses of tissue culture?

  Used to clone plants that don't readily reproduce or are endangered or rare.

  
  

  Also used to grow whole plants from genetically engineered plant cells.
• What is micropropagation?


  When tissue culture is used to produce lots of cloned plants very quickly.

  
  

  Cells are taken from developing cloned plants and subcultured (grown on another fresh culture medium) - repeating this process creates dozens of clones.

  
  

  This technique is used extensively in horticulture and agriculture, e.g. to produce fields full of a crop that has been gentically engineered to be pest-resistant.
• What are the arguments for artifical plant cloning?

  Desirable genetic characteristics are always passed on to clones.

  
  

  Tissue culture allows plants to be reproduced in any season because the environment is controlled.

  
  

  Less space is required by tissue culture than would be needed to produce the same number of plants by conventional growing methods.

  
  

  Produces lots of plants quickly compared to the time it would take to grow them from seeds.
• What are the arguments against artificial plant cloning?

  Undesirable genetic charcateristics are always passed on to clones.

  
  

  Cloned plant populations have no genetic variability, so a single disese could kill them all.

  
  

  Production costs of tisse culture are very high due to high energy use and the training of skilled workers, so it's unsustainable for small scale production.

  
  

  Contamination by microorganisms during tissue culture can be disastrous and result in complete loss of the plants being cultured.
• What is artificial embryo twinning?

  1. An egg cell is extracted from a female cow and fertilised in a Petri dish.

  
  

  2. The fertilised egg is left to divide at least once, forming an embryo in vitro.

  
  

  3. Next, the individual cells from the embryo are separated and each is put into a separate Petri dish. Each cell divides and develops normally, so an embryo forms in each Petri dish.

  
  

  4. The embryos are them implanted into female cows, which act as surrogate mothers.

  
  

  5. The embryos continue to develop insode the surrogate cows, and eventually the offspring are born. They're all genetically identical to each other.

  
• What is somatic cell nuclear transfer SCNT?

  1. A somatic cell (any cell that isn't a reproductive cell) is taken from sheep A. The nucleus is extrcated and kept.

  
  

  2. An oocyte (immature egg cell) is taken from sheep B. Its nucleus is removed to form an enucleated oocyte.

  
  

  3. The nucleus from sheep A is inserted into the enucleated oocyte - the oocyte from sheep B now contains the genetic info from sheep A.

  
  

  4. The nucleus and enucleated oocyte are fused together and stimulated to divide, e.g. by electrofusion, where an electrical current is applied. this produces an embryo.

  
  

  5. Then the embryo is implanted into a surrogate mother and eventually a lamb is born that's a clone of sheep A.

  
• What are the uses of animal cloning?

  Scientists use cloned animals for research purposes - e.g. they can test new drugs on cloned animals and the variables that come from genetic differences are removed.

  
  

  Cloning can be used in agriculture so farmers can increase the number of animals with desirable characteristics to breed from.

  
  

  Animals that have been genetically modified to produce a useful substance that they wouldn't normally produce could be cloned to produce lots of identical animals that all produce the same substance.

  
  

  Cloning can also be used to save endangered animals from extinction by cloning new individuals.
• Why would scientists only want the cloned embryonic stem cells?

  The cells are harvested from young embryos and have the potential to become any cell type, so scientists think they could be used to replace damaged tissues in a range of diseases.

  
  

  If replacement tissue is made from cloned embryonic stem cells that are genetically identical to the patient's own cells, it won't be rejected by the immune system.
• What are the arguments for animal cloning?

  Desirable characteristics are always passed on to clones.

  
  

  Infertile animals can be reproduced, so if a farmer's prize-winning cow was infertile for any reason, they could still reproduce it.

  
  

  Animals can be cloned at any time - you wouldn't have to wait until a breeding season to get new animals.

  
  

  Increasing the population of endangered species helps to preserve biodiversity.

  
  

  Cloning can help us develop new treatments for disease, which could mean less suffering for some people.
• What are the arguments against animal cloning?

  It's difficult, time-consuming and expensive.

  
  

  There's no genetic variability in cloned populations, so undesirable genetic characteristics are always passed on to clones. This means that all the cloned animals in a population are susceptible to the same diseases. Potentially, a single disease could wipe them all out.

  
  

  Some evidence suggests that clones may not live as long as natural offspring. Some think this is unethical.

  
  

  Using cloned human embryos as a source of stem cells is controversial. The embryos are usually destroyed after the embyronic stem cells have been harvested - some people think this is unethical.
• What is biotechnology?

  The industrial use of living organisms to produce food, drugs and other products.

  
  

  The living organisms used are mostly microorganisms.
• Why are the living organisms used mostly microorganisms?

  Their ideal growth conditions can be easily created.

  
  

  Due to their short life cycle, they grow rapidly under the right conditions, so products can be made quickly.

  
  

  They can grow on a range of inexpensive materials - this makes them economical to use.

  
  

  They can be grown at any time of the year.
• How are enzymes used in biotechnology?

  Enzymes used in industry can be contained within the cells of microorganisms - these are called intracellular enzymes.

  
  

  Enzymes are also used that aren't contained within cells - thse are called isolated enzymes.

  
  

  Some are secreted naturally by microorganisms, but others have to be extracted.

  
  

  Naturally secreted enzymes are cheaper to use because it can be expensive to extract enzymes from cells.
• How are microorganisms used in making beer?

  Yeast is added to a type of grain and other ingredients.

  
  

  The yeast respires anaerobically using the glucose from the grain and produces ethanol and carbon dioxide. This is called fermentation.
• How are microorganisms used in baking?

  Yeast is used to make bread rise.

  
  

  The carbon dioxide produced by fermentation of sugars in the dough make sure it doesn't stay flat.
• How are microorganisms used in cheese making?

  Cheese production used to rely on a substance called rennet.

  
  

  Rennet contains the enzyme chymosin, which clots the milk.

  
  

  Chymosin can be obtained from yeast cells that have been genetically modified to produce the enzyme.

  
  

  Cheese making also involves lactic acid bacteria.

  
  

  These bacteria convert the lactose in milk to lactic acid, which makes it turn sour and contributes to it solidifying.

  
  

  The production of blue cheese also involves the addition of fungi to make the characteristic blue veins.
• How are microorganisms involved in yoghurt production?

  Involves the use of lactic acid bacteria to clot the milk and cause it to thicken.

  
  

  This creates a basic yoghurt product and any flavours and colours are added.
• How are microorganisms involved in penicillin production?


  In times of stress, a fungus produces an antibiotic, penicillin, to stop bacteria from growing and competing for resources.

  
  

  To produce on a massive scale, the fungus of the Penicillium genus is grown under stress in industrial fermenters and the penicillin produced is collected and processed to be used in medicine.
• How are microorganisms used in insulin production?

  Insulin is made by genetically modified bacteria, which have the gene for human insulin production inserted into their DNA.

  
  

  These bacteria are grown in an industrial fermenter on a massive scale and the insulin produced is collected and purified.
• How are microorganisms used in bioremediation?

  Posh name for the process of using organisms to remove pollutants, like oil or pesticides, from contaminated sites.

  
  

  Most commonly, pollutant-removing bacteria that occur naturally at a site are provided with extra nutrients and enhanced growing conditions to allow them to multiply and thrive.

  
  

  These bacteria break down the pollutants into less harmful products, cleaning up the area.
• How can microorganisms be used as a food source for humans?

  Can be grown as a source of protein, which can act as a valuable food source.

  
  

  This is called single-cell protein.
• What are the advantages of producing food for human consumption from microorganisms?

  Microorganisms used to make single-cell protein can be grown using many different organic substrates, including waste materials such as molasses.

  
  

  They can be grown quickly, easily and cheaply. Production costs are low because they have simple growth requirements, can be grown on waste product and less land is required in comparison to growing crops or rearing livestock.

  
  

  Microorganisms can be cultured anywhere if you have the right equipment. This means a food source could be readily produced in places where growing crops and rearing livestock is difficult.

  
  

  Single-cell protein is often considered a healthier alternative to animal protein.
• What are the disadvantages of producing food for human consumption from microorganisms?


  Because the conditions needed to grow the desired microorganism are also ideal for other microorganisms, a lot of effort has to go into making sure that the food doesn't get contaminated with unwanted bacteria.

  
  

  People may not like the idea of eating food that has been grown using waste products.

  
  

  Single-cell protein doesn't have the same texture or flavour as real meat.

  
  

  If single-cell protein is consumed in high quantities, health problems could be caused due to high levels of uric acid released when the large amounts of amino acids are broken down.
• What are the two main methods for culturing microorganisms?

  Batch fermentation

  
  

  Continuous fermentation

  
• What is batch fermentation?

  Where microorganisms are grown in individual batches in a fermentation vessel.

  
  

  When one culture ends it is removed and then a different batch of microorganisms is grown in the vessel.

  
  

  This is known as a closed culture,