Midterm 3 Review

• Gene


  A region of DNA that codes for a certain protein and thus a certain trait type
• Allele


  A version of a gene that codes for a specific protein and thus a specific trait
• Genome


  Aggregation of all DNA within a target cell, organism, species (shifts depending on the scope of the study)

  
• Genotype


  DNA of a target
• Phenotype


  The physical characteristics of an organism
• Sister chromatids


  Identical chromatids following DNA replication
• Homologous Chromosomes


  Chromosomes with the similar set of genes
• DNA is genetic material / genetic code
• Central Dogma


  DNA → mRNA → Polypeptide Chain → Protein
• Nucleotide


  5' Phosphate + 5-C sugar (pentose) + Nitrogenous Base
• Nucleotides will have a 3' Hydroxyl. The 5' Phosphate and 3' Hydroxyl determine the 5' to 3' directionality
• DNA is double stranded with the stands going in opposite direction yet parallel (Antiparallel)
• Nucleotides can bond in any order along (within) a strand with phosphodiester bonds
• Nucleotides bond C-G and A-T (or A-U) between the strands with Hydrogen bonds
• Differing number of Hydrogen bonding sites determines the pairing of the nucleotides for hydrogen bonding
• Chromatin


  Shape of DNA that is loosely bound and available for transcription or replication

  
• Chromosome


  Shape of DNA that is tightly bound (super coiled) and not available for transcription or replication. Able to be easily separated from other chromosomes during cell division

  
• DNA is found wrapped around Histone Proteins. These proteins allow for the DNA to change shape more easily

  
• Chromatid


  Complete DNA strand
• During replication the DNA amount doubles while the chromosome number is held constant

  
• Models of Replication


  • Conservative model
  • Semi-Conservative model
  • Dispersive/Non-Conservative model
• DNA is replicated semi-conservatively. This means that each DNA molecule is made up of 1 template/original strand and 1 newly synthesized strand

  
• Origin of replication (ORI)


  Sites where DNA replication begins

  
• Replication bubble


  1. The strands of the DNA split apart forming a replication bubble

  2. This bubble expands outward as DNA is replicated

  
• Replication fork


  The site where DNA separates

  
• Leading strand


  DNA can be continuously replicated (moving left by going left)

  
• Lagging strand


  DNA is replicated piecewise with multiple start points (moving right by going left)
• DNA is replicated in the 5' → 3' direction of the new strand

  
• Helicase


  Separates the two strands
• Single-Stranded Binding Proteins (SSBP)


  Keeps separated strands apart
• Topoisomerase


  Relieves structural stress of the DNA ahead of the replication fork (not in the bubble)
• Primase


  Places RNA primers that serve as the signal to start DNA replication (sets start points)

  
• DNA Polymerase 3 (Pol III)


  Places DNA nucleotides starting at a primer

  
• DNA Polymerase 1 (Pol I)

  Removes RNA primer and replaces it with DNA
• DNA Ligase (Ligase)


  Binds fragments together
• The Hershey-Chase experiment proved that DNA was the genetic material
• The Meselson-Stahl experiment proved that DNA replication is semi-conservative

  
• Mutation


  Mistakes in DNA replication

  
• Mutations can cause the gene product to be changed, this can increase or decrease its activity
• Mutations are the reason why organisms evolve and are different from each other