BIOL 107A - M1

• DNA, RNA and Protein are all considered macromolecules
• What is Mendel's Law of Inheritance?

  Mendel proposed that inheritance was particulate (has clear characteristics) and was not blended
• Genes exist in paired forms (genes) and are segregated into gametes
• What is Independent segregation?

  allele of one gene separates independently of an allele of another gene - only one of the two gene copies present in an organism is distributed to each gamete
• What does it mean if the gene is on the same chromosome?

  Linked
• What if the characteristics are not on the same chromosome?

  They are independent and do not affect each other
• Chromosomes are located in the nucleus
• Nuclei are rich in phosphorus, oxygen, nitrogen, carbon, and hydrogen (components of DNA)
• What is the conclusion of Frederick Griffith's experiment?

  R bacteria (non-lethal) transformed into S bacteria (lethal) due to the coating, allowing the bacteria to transform and multiply
• Why was the R bacteria able to transform into S bacteria in Griffith's experiment?

  R bacteria are attacked by the immune system.

  S bacteria's coating protects them from the immune response because it mimics mammalian cells.
• What is the process of R bacteria turning into S bacteria?

  Transformation
• Who used fractionation in their experiment?

  Avery, MacLeod, McCarty
• What did Avery, MacLeod, and McCarty's experiment prove?

  DNA was sufficient to cause transformation
• Avery et al. added enzymes that degrade RNA, DNA, Protein, and Polysaccharides using a negative experiment
• What is a negative experiment?

  Treat every part of the cell and observe if there is a transformation. If there is NO transformation, it means that a specific component is a factor for transformation.
• Avery et al. treated bacteria with DNase and it resulted in NO transformation, what does this mean?

  DNA was removed from bacteria, this implies DNA is the transformation factor
• Packaging of the eukaryotic genome

  1. DNA is packed into chromatin (DNA+histones)

  2. Genomes are composed of chromosomes in cells

  
• Chromatin


  Composed of DNA and histones
• Nucleosomes


  Repeating structural element in eukaryotic chromosomes, core octamer of histones plus one molecule of the linker histone, 180 bp DNA wound around, left-handed

  
• Histones


  Small, positively-charged, basic proteins. Histones H2A, H2B, H3, and H4. Rich in arginine and lysine. 146 bp of negatively charged DNA wraps nearly twice around the positively charged octamers

  
• Linker histones


  Slightly larger, positively-charged, basic proteins and occur between core octamers

  
• Most eukaryotes package their genomes with histones
• Carboxyl (C) terminal end of histones


  Extended histone-fold domain, Histone-histone interactions, Histone-DNA interactions
• Amino (N) terminal charged "tails" of histones


  Lysine-rich, Sites of many post-translational modifications
• Which model is favored? Classic solenoid model or zig-zag ribbon model

  
  

  zig-zag ribbon
• Fully condensed: metaphase chromosomes


  Packing ratio of 10,000-fold

  
• Centromere

  Provides the site of attachment for segregation during cell division

  
• Karyotype


  The number, size, and shape of the chromosomes

  
• Heterochromatin

  Chromatin that is condensed and suppresses transcription

  
• Euchromatin


  Chromatin that is more open and allows for gene activation

  
• Eukaryotic gene expression regulation

  • DNA sequence: DNA-binding proteins associate with regulatory elements in the DNA
  • Chromatin structure: changes in the way the DNA is wrapped around the histones
  • Nuclear architecture: positioning of chromosomes in "territories" in the nucleus

  
• The majority of the eukaryotic genome is noncoding
• Classes of repetitive DNA sequences

  • Interspersed elements
  • Tandem repetitive elements
• Interspersed elements


  Genome-wide repeats that are primarily degenerate copies of transposable elements, Short interspersed nuclear elements (SINEs), Long interspersed nuclear elements (LINEs)

  
• Tandem repetitive sequences

  Arranged in arrays with variable numbers of repeats, Satellite DNA, Minisatellites, Short tandem repeats (STRs)
• Satellite DNA

  Very highly repetitive DNA with repeat lengths of one to several thousand base pairs, Buoyant density during density gradient centrifugation differs from that of the bulk of the DNA
• Lateral gene transfer


  Transfer of DNA between two different species, especially distantly related species, Important mechanism for bacterial evolution, Associated with the gradual loss of an endosymbiont's independence on the path to becoming an organelle
• Organelle genomes reflect an endosymbiont origin
• Most human genes were transferred from an endosymbiont
• Eukaryotic genomes are mosaic