molecular genetics

• Mendel


  Discovered Genotypes and Phenotypes
• Miescher


  Noticed a part of a cell that didn't act like protein (nucleus)
• Griffith


  Realized that strain can exchange DNA and become new strains
• Hershey and Chase


  When bacteriophages, which are composed of DNA and protein, infect bacteria, their DNA enters the host bacterial cell, but most of their protein does not
• Franklin, Wilkins, Watson & Crick


  Discovered the shape of DNA
• Chargaff


  Discovered base pair
• DNA Replication


  1. Separation of DNA (unwinding and unzipping)

  2. Primase and DNA Polymerase III Base Pairing

  3. Editing with DNA Polymerase I and Ligase
• Frameshift mutations


  Mutations that occur when the addition or deletion of nucleotides causes a shift in the reading frame of the mRNA sequence, leading to a completely different amino acid sequence from the point of mutation onwards
• Silent mutations


  Mutations that do not result in any change to the amino acid sequence of a protein due to the redundancy of the genetic code. They can still have effects on mRNA stability or splicing efficiency
• Missense mutations


  A type of point mutation where a single nucleotide change in the DNA sequence results in a codon that codes for a different amino acid in the protein product
• Lysing


  1. To analyze DNA we must first lyse cells and get the DNA out

  2. We use enzymes such as lysozyme, ProtK, soap and buffers

  3. Lysozyme breaks the cell and soap helps separate the parts inside (ER, Mito,...)

  4. The solution is centrifuged to remove some of the heavy cell parts which form a pellet at the bottom of the test tube. DNA is in solution

  5. Next precipitate DNA with cold ethanol (-20ºC)
• Restriction Enzymes


  Enzymes produced by bacteria such as E.coli (e.g. EcoR1) that cut DNA at a specific sequence
• Restriction Fragment Length Polymorphism (RFLP)


  DNA is cut to many different sizes. Every person has their own pattern. Can be used to identify suspects from cells at a crime scene or for paternity cases
• Electrophoresis


  1. A technique used to separate DNA or any other small molecules

  2. A current passes through a buffer solution from the anode (-) to the cathode (+)

  3. As the current travels between the electrodes the DNA is pulled through the gel toward the cathode since DNA is negatively charged

  4. Different sizes of DNA move at different speeds so fragment sizes separate
• Reading Gels


  1. You can't see the DNA so it must be stained and looked at under UV light

  2. Each band represents a DNA fragment size

  3. Compare the bands. Some gels have "ladders"
• Polymerase Chain Reaction (PCR)

  1. Heating DNA to 95C denatures it separating the double helix

  2. 2 different Primers anneal to each template strand at 65C

  3. With dNTPs and Taq polymerase the complimentary strand is made as the solution heats to 72C
• Problems with PCR


  • Sample purity. The slightest contamination could provide false positives
  • Taq polymerase makes more mistakes than most other polymerase
  • The longer the fragment the less reliable the copying
• Sanger Method: DNA Sequencing


  1. Denature dsDNA

  2. Anneal primers

  3. Add nucleotides and dideoxynucleotides

  4. Run fragments on an electrophoresis on Polyacrylamide gel