genetic engineering

• selective breeding


  the process of artificially selecting organisms with desired traits to be parents of the next generation
• why is selective breeding used?

  scientists are able to use organisms with beneficial traits and mutations for reproduction, and the positive mutations are spread out and variation occurs
• what traits are desirable in organisms?

  - animals that produce more meat, milk or eggs

  - crops with disease resistance

  - dogs with a gentle temperament

  - decorative plants with large or unique flowers
• selective breeding process


  - parents with desired characteristics are chosen

  - they are bred together

  - from the offspring those with desired characteristics are bred together

  - the process is repeated many times over several generations until all the offspring have the desired characteristic
• why is selective breeding used in agriculture?


  to improve yields
• drawback of selective breeding

  reduced gene pool causing inbreeding and a lack of variation in species
• inbreeding


  continued breeding of individuals that are closely related with similar characteristics
• Why is inbreeding a problem?

  it causes health problems because there's more chance of organisms inheriting defective recessive genes when the gene pool is too limited, resulting in genetic disorders
• why is a lack of variation in species a problem?

  if climate changes or new disease emerges and an organism dies to these changes, the others are also likely to die to it
• gene pool


  all the genes, including all the different alleles for each gene, that are present in a population at any one time
• genetic engineering


  a technology that includes the process of manipulating or altering the genetic material of a cell resulting in desirable functions or outcomes that would not occur naturally
• genetic engineering process


  - desired gene cut out using restriction enzymes

  - this gene is then inserted into a vector, which is usually a virus or a bacterial plasmid, depending on the type of organism the gene is being transferred to

  - when the vector is introduced to the target organism, the useful gene is inserted into its cell(s)
• why is genetic engineering carried out?

  to modify the genetic makeup of organisms, typically to introduce desired traits or characteristics
• instances of genetic engineering

  - bacteria have been genetically modified to produce human insulin that can be used to treat diabetes

  - genetically modified crops have had their genes modified to improve the size/quality of their fruit r make them resistant to disease, insects and herbicides

  - sheep's have been genetically engineered to produce substances, like drugs, in their milk that can be used to treat human disease

  - scientists are researching genetic modification treatments for inherited diseases caused by faulty genes
• gene therapy


  the insertion of working copies of a gene into the cells of a person with a genetic disorder in an attempt to correct the disorder
• gene transfer in early stages of development

  the transfer of the gene may be carried out when the organism receiving the gene is at an early stage of development (e.g. egg or embryo), meaning that the organism develops with the characteristic coded for by the gene
• pros of genetically modifying crops

  - can increase yield, making more food

  - could be engineered to contain nutrients people in poverty are missing

  - they are already being grown in some places, often without any problems
• cons of genetically modifying crops

  - may affect the number of wildflowers that live in and around crops - reduces farmland biodiversity

  - some people don't believe they are safe

  - concerns over the effect they have on human health

  - transplanted genes may get out into the natural environment
• cloning


  a process in which a cell, cell product, or organism is copied from an original source.
• why is cloning used?

  for organ donation, reducing the number of endangered species and producing organisms with desirable traits
• how can plants be cloned?

  tissue culture and cuttings
• tissue culture cloning


  a few plant cells are put in a growth medium with hormones and they grow into new plants (which are clones of the parent plant) - these can be made very quickly, in very little space and can be grown all year
• why is tissue culture used?

  done by scientists to preserve rare plants that are hard to reproduce naturally and by plant nurseries to produce lots of stock quickly
• cuttings cloning


  gardeners take cuttings from good parent plants, and then plant them to produce genetically identical clones of parent plants - these plants can be produced quickly and cheaply
• how can animals be cloned

  embryo transplants and adult cell cloning
• embryo transplants


  sperm cells and egg cells are chosen from the best animals and the sperm then artificially fertilises the egg, in which the embryo is then split many times to form clones (before any cells become specialised) and implanted into many other animals where they will grow into genetically identical offspring
• adult cell cloning


  process in which the nucleus of an adult cell of one animal is inserted into an unfertilised egg cell from another animal. the egg cell is then stimulated by an electric shock, making it divide just like a normal embryo and when the embryo is a ball of cells, it is implanted into the womb of an adult female and then grows into a genetically identical clone of the original adult body cell as it has the same genetic information
• pros of cloning


  - study of animal clones leads to greater understanding of embryo development, ageing and age related disorders

  - preserve endangered species
• cons of cloning


  - reduced gene pool

  - animals may be less healthy

  - worries that humans could be cloned and born with severe health problems