BIOLOGY 2

• Classical plant breeding


  Uses deliberate interbreeding (crossing) of closely or distantly related individuals to produce new crop varieties or lines with desirable properties
• Genetic engineering


  The process of using recombinant DNA (rDNA) technology to alter the genetic makeup of an organism
• Genetic engineering


  1. Introduction of new traits into an organism

  2. Enhancement of a present trait by increasing the expression of the desired gene

  3. Enhancement of a present trait by disrupting the inhibition of the desired genes' expression
• Recombinant DNA

  1. Cutting or cleavage of DNA by restriction enzymes

  2. Selection of an appropriate vector or vehicle

  3. Ligation of the gene of interest with the vector

  4. Transfer of the recombinant plasmid into a host cell

  5. Selection process to screen which cells actually contain the gene of interest

  6. Sequencing of the gene to find out the primary structure of the protein
• Biolistics


  A technique where a "gene gun" is used to fire DNA-coated pellets on plant tissues
• Heat Shock Treatment


  A process used to transfer plasmid DNA into bacteria by increasing the pore sizes of their plasma membranes
• Electroporation


  A technique that uses an electric "shock" to expand the membrane pores for insertion of genes into mammalian cells
• Methods for selection and screening of transformants/GMOs

  • Selection of plasmid DNA containing cells
  • Selection of transformed cells with the desired gene
  • PCR detection of plasmid DNA
• Genetically Modified Organisms (GMOs)


  Organisms that have been modified through genetic engineering
• Genetic engineering involves the direct manipulation of one or more genes, often by adding a gene from another species to give the organism a desired phenotype
• Classical plant breeding uses deliberate interbreeding to produce new crop varieties with desirable properties
• Genetic engineering is the process of using recombinant DNA technology to alter the genetic makeup of an organism
• Recombinant DNA technology involves cutting DNA with restriction enzymes, selecting a vector, ligating the gene of interest to the vector, transferring the recombinant plasmid to a host cell, and screening for the desired transformants
• Biolistics, heat shock treatment, and electroporation are methods used to introduce plasmids containing foreign genes into host cells
• Precambrian


  The largest division of the geologic time scale
• Eras in the geologic time scale

  • Precambrian
  • Paleozoic
  • Mesozoic
  • Cenozoic
• Periods under the Paleozoic era

  • Cambrian
  • Ordovician
  • Silurian
  • Devonian
  • Carboniferous
  • Permian
• Periods under the Mesozoic era


  • Triassic
  • Jurassic
  • Cretaceous
• Periods under the Cenozoic era

  • Tertiary
  • Quaternary
• Cambrian Explosion


  Sudden, apparent explosion of diversity in life forms about 545 million years ago
• Types of fossils


  • Molds
  • Casts
  • Petrified
  • Original Remains
  • Carbon Film
  • Trace/ Ichnofossils
• Relative dating


  Compares fossils as older or younger based on their position in rock layers, does not tell exact age
• Absolute dating


  Determines the actual age of the fossil using radiometric dating and radioactive isotopes
• The geologic time scale is subdivided into 4 groups from largest to smallest: Eons, Eras, Periods, Epochs
• The end of the Mesozoic era was believed to be caused by a comet or asteroid colliding with Earth
• Genetic variation


  The prerequisite and should therefore be present for any genetic process to cause change in populations from generation to generation
• Hardy-Weinberg Principle


  A principle that states that in an infinitely large, interbreeding population in which mating is random and in which there is no selection, migration, or mutation, gene and genotype frequencies will remain constant from generation to generation
• Conditions for Hardy-Weinberg equilibrium

  • No mutation (change) in the DNA sequence
  • No migration (moving into or out of a population)
  • A very large population size
  • Random mating
  • No natural selection
• Calculating gene and genotype frequencies using the Hardy-Weinberg equation


  1. p2 + 2pq + q2 = 1

  2. Where p is the frequency of the "A" allele and q is the frequency of the "a" allele in the population

  3. p2 represents the frequency of the homozygous genotype AA

  4. q2 represents the frequency of the homozygous genotype aa

  5. 2pq represents the frequency of the heterozygous genotype Aa
• Natural selection, genetic drift, and gene flow are the mechanisms that cause changes in allele frequencies over time
• Natural selection


  • Occurs when individuals with certain genotypes are more likely than individuals with other genotypes to survive and reproduce, and thus to pass on their alleles to the next generation
  • Requires variation among individuals within a population in some trait, this variation is heritable, and variation in this trait is associated with variation in fitness
• Mutation


  • Although mutation is the original source of all genetic variation, mutation rate for most organisms is pretty low, so the impact of brand-new mutations on allele frequencies from one generation to the next is usually not large
• Gene flow


  • Involves the movement of genes into or out of a population, due to either the movement of individual organisms or their gametes
• Genetic drift


  • Involves changes in allele frequency due to chance events - literally, "sampling error" in selecting alleles for the next generation, and has a stronger effect on small populations
• When one or more of the mechanisms of natural selection, genetic drift, and gene flow are acting in a population, the population violates the Hardy-Weinberg assumptions, and evolution occurs
• Species


  In biology, classification comprising related organisms that share common characteristics and are capable of interbreeding
• Reproductive isolating mechanisms


  • Geographic or ecological or habitat isolation
  • Temporal or seasonal isolation
  • Behavioral isolation
  • Mechanical isolation
  • Gametic isolation
• Pre-zygotic isolation mechanisms


  Prevent fertilization and zygote formation
• Post-zygotic isolation mechanisms


  Allow fertilization but nonviable or weak or sterile hybrids are formed
• Modes of speciation


  • Allopatric speciation or geographic speciation
  • Sympatric speciation
  • Parapatric speciation