1.2

• What is variation in a population?

  Differences in characteristics of individuals
• What are the two main causes of variation within a species?

  Genetics and environment
• What is genetic variation?

  Variations in genotypes due to different alleles
• What creates genetic variation in a species?

  Spontaneous mutations and sexual reproduction
• What is a mutation?

  A random change to the DNA base sequence
• What is variation?

  Differences in the characteristics of individuals in a population
• What are the two causes of variation within a species?

  Genetics and environment
• What is genetic variation?

  Variations in the genotypes of organisms of the same species due to the presence of different alleles
• What is a mutation?

  A random change to the base sequence in DNA which results in genetic variants
• State the three types of gene mutation.

  Insertion, deletion, substitution
• How may a gene mutation affect an organism's phenotype?

  Neutral mutation does not change the sequence of amino acids, minor change in phenotype, or severe change in phenotype
• What is the consequence of a new phenotype caused by a mutation being suited to an environmental change?

  There will be a rapid change in the species
• What is evolution?

  A gradual change in the inherited traits within a population over time due to natural selection which may result in the formation of a new species
• Outline the theory of natural selection.

  All species evolved from simple life forms, genetic variation exists due to mutations, selection pressures exist, random mutation gives an organism a selective advantage, organism with advantage survives and reproduces passing on beneficial alleles, frequency of advantageous alleles increase
• How do two populations become different species?

  When their phenotypes become different to the extent that they can no longer interbreed to produce fertile offspring
• What is selective breeding?

  The process by which humans artificially select organisms with desirable characteristics and breed them to produce offspring with similar phenotypes
• Outline the main steps involved in selective breeding.

  Identify a desired characteristic, select parent organisms with the desired traits and breed them, select offspring with the desired traits and breed them, repeat the process until all offspring have the desired traits
• Give examples of characteristics selected for in selective breeding.

  Disease resistance in crops, higher milk or meat production in animals, gentle nature in domestic dogs, large flowers
• What is the main advantage of selective breeding?

  Creates organisms with desirable features like higher crop yields, greater milk supply, larger fruit, and more docile domesticated animals
• Other than in agriculture, where else is selective breeding useful?

  In medical research and in sports e.g. horse racing
• Outline the disadvantages of selective breeding.

  Reduction in the gene pool, inbreeding resulting in genetic disorders, development of physical problems, potential to select harmful recessive alleles
• What is genetic engineering?

  The modification of the genome of an organism by the insertion of a desired gene from another organism
• Give an example of uses for genetically modified plants.

  Disease resistance and produce larger fruits
• What is a use for genetically modified bacteria cells?

  To produce human insulin to treat diabetes mellitus
• Describe the benefits of genetic engineering.

  Increased crop yields, useful in medicine, and production of scarce resources
• Describe the risks of genetic engineering.

  Long-term effects of consumption unknown, negative environmental impacts, late-onset health problems in GM animals, and expensive GM seeds
• What is the name for crops that have had their genes modified?

  Genetically modified (GM) crops
• How is genetic engineering used to protect crops against insects?

  The gene for toxin production in Bt can be isolated and inserted into the DNA of crops, so Bt crops now secrete the toxin which kills any insect larvae that feed on it
• What is Bacillus thuringiensis (Bt)?

  A bacterium which secretes a toxin that kills insect larvae
• What are the benefits of Bt crops?

  Increased crop yields, lessens the need for artificial insecticides, and Bt toxin is specific to certain insect larvae so is not harmful to other organisms
• What are the risks of Bt crops?

  Long term effects of consumption unknown, insect larvae may become resistant to the Bt toxin, and killing insect larvae reduces biodiversity
• What is a vector?

  A structure that delivers the desired gene into the recipient cell e.g. plasmids, viruses
• Describe the process of genetic engineering.

  DNA is cut at specific base sequences by restriction enzymes to create sticky ends, vector DNA cut using the same restriction enzymes to create complementary sticky ends, ligase enzymes join the sticky ends of the DNA and vector DNA forming recombinant DNA, recombinant DNA mixed with and 'taken up' by target cells
• What are the main components of genetic variation?

  • Genetics
  • Environment
• What are the steps of the process of natural selection?

  1. All species evolved from simple life forms
  2. Genetic variation exists due to spontaneous mutations
  3. Selection pressures (e.g. competition, disease) exist
  4. Random mutation gives an organism a selective advantage
  5. Organism with advantage survives and reproduces, passing on beneficial alleles
  6. Frequency of advantageous alleles increase
• How does selective breeding work?

  1. Identify a desired characteristic
  2. Select parent organisms with the desired traits and breed them
  3. Select offspring with the desired traits and breed them
  4. Repeat the process until all offspring have the desired traits
• What are the pros and cons of genetic engineering?

  Pros:

  • Increased crop yields
  • Useful in medicine (e.g. insulin production)
  • Production of scarce resources (e.g. vitamin A in golden rice)

  
  

  Cons:

  • Long-term effects of consumption unknown
  • Negative environmental impacts (e.g. biodiversity loss)
  • Late-onset health problems in GM animals
  • Expensive GM seeds
• What are the benefits and risks of Bt crops?

  Benefits:

  • Increased crop yields
  • Lessens need for artificial insecticides
  • Bt toxin is specific to certain insect larvae

  
  

  Risks:

  • Long term effects of consumption unknown
  • Insect larvae may become resistant to Bt toxin
  • Killing insect larvae reduces biodiversity
• How does genetic engineering protect crops against insects?

  • The gene for toxin production in Bt bacteria is isolated
  • This gene is inserted into the DNA of crops
  • The Bt crops now secrete the toxin which kills any insect larvae that feed on them