Variation and Evolution

• What is variation in a population?

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

  Genetics, environment, or both
• 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 are the three types of gene mutation?

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

  No change in amino acid sequence occurs
• How may a mutation cause a minor change in phenotype?

  It may change traits like eye color
• What can happen if a mutation completely changes the amino acid sequence?

  It may result in a non-functional protein
• What is the consequence of a new phenotype being suited to an environmental change?

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

  A gradual change in inherited traits over time
• What drives evolution?

  Natural selection leading to new species
• Outline the theory of natural selection.

  1. Genetic variation exists due to mutations.
  2. Selection pressures exist (e.g., competition).
  3. Random mutation gives a selective advantage.
  4. Organism adapts and survives.
  5. Organism reproduces, passing on beneficial alleles.
  6. Frequency of advantageous alleles increases.
• How do two populations become different species?

  They can no longer interbreed to produce fertile offspring
• What is selective breeding?

  Humans breed organisms with desirable traits
• Outline the main steps involved in selective breeding.

  1. Identify a desired characteristic.
  2. Select parent organisms with desired traits.
  3. Breed selected offspring together.
  4. Repeat until all offspring have desired traits.
• What is the main advantage of selective breeding?

  Creates organisms with desirable features
• Where else is selective breeding useful besides agriculture?

  In medical research and sports
• Outline the disadvantages of selective breeding.

  • Reduction in gene pool.
  • Inbreeding leads to genetic disorders.
  • Development of physical problems.
  • Selection of harmful recessive alleles.
• What is genetic engineering?

  Modification of an organism's genome by gene insertion
• What is a use for genetically modified bacteria cells?

  To produce human insulin for diabetes
• Describe the benefits of genetic engineering.

  • Increased crop yields for growing populations.
  • Useful in medicine (e.g., insulin).
  • GM crops produce scarce resources (e.g., vitamin A).
• Describe the risks of genetic engineering.

  • Unknown long-term effects of GM crops.
  • Negative environmental impacts (e.g., biodiversity loss).
  • Late-onset health problems in GM animals.
  • High costs of GM seeds for LEDCs.
• What is the name for crops that have had their genes modified?

  Genetically modified crops
• What are inherited disorders being explored in?

  Medical research
• What does GM golden rice produce?

  Beta-carotene, a source of vitamin A
• What are the risks of genetic engineering?

  1. Long-term effects of GM crop consumption unknown
  2. Negative environmental impacts (biodiversity reduction)
  3. Late-onset health problems in GM animals
  4. High cost of GM seeds for LEDCs
• What is the name for crops that have had their genes modified?

  Genetically modified (GM) crops
• What is Bacillus thuringiensis (Bt)?

  A bacterium that kills insect larvae
• How is genetic engineering used to protect crops against insects?

  1. Isolate the gene for toxin production in Bt
  2. Insert the gene into crop DNA
  3. Bt crops secrete toxin to kill insect larvae
• What are the benefits of Bt crops?

  1. Increased crop yields
  2. Reduced need for artificial insecticides
  3. Specificity of Bt toxin to certain larvae
• What are the risks of Bt crops?

  1. Unknown long-term effects of Bt crop consumption
  2. Potential resistance of insect larvae to Bt toxin
  3. Reduction in biodiversity from killing larvae
• Describe the process of genetic engineering.

  1. Cut DNA at specific sequences with restriction enzymes
  2. Cut vector DNA with the same enzymes
  3. Join sticky ends with ligase enzymes to form recombinant DNA
  4. Mix recombinant DNA with target cells
• What is a vector in genetic engineering?

  A structure that delivers desired genes
• How can plants be cloned?

  1. Taking plant cuttings
  2. Tissue culture
• What is tissue culture?

  Growing identical new plants from small cell groups
• Describe how plants are grown using tissue culture.

  1. Select a plant with desired traits
  2. Cut small samples from meristem tissue
  3. Grow in a petri dish with growth medium
  4. Transfer to compost for further growth
• What must be ensured when preparing tissue cultures?

  Aseptic conditions to prevent contamination
• What does the growth medium contain?

  Nutrients and growth hormones
• What are the advantages of growing plants by tissue culture?

  1. Fast and simple process
  2. Requires little space
  3. Produces many identical clones
  4. Useful for preserving endangered species