Week 1: Water + DNA Flashcards
Which direction does the dipole go in water?
Towards the oxygen (more negative: 2 unshared electron pairs)
Hydrogen has positive dipole
What are H-bonds responsible for?
- Stability + structure of nucleic acid
- Used in most enzymatic reactions
- Transfer of electrons, chemical groups + substrates
When was genetic material discovered?
1944 when Ostwald Avery worked out what type of macromolecule genetic material was (DNA).
Explain the Hershey-Chase experiment
- E. coli cells were infected with each virus
- Cells were centrifuged
- Cells with phosphorus = DNA // No sulfur = proteins
- This meant infecting agent was DNA
What is a pyrimidine?
Single six-membered aromatic ring (C,T,U)
What is a purine?
Have a double ring (larger) (G,A)
Are nucleotide polynucleotides known as acids or bases?
Acids
What are the ‘Chargaff Rules’?
A-T has 2 H-bonds, C-G have 3 H-bonds.
What are the 2 main characteristics of DNA?
It is soluble and acidic
What are the bonds that join nucleotides in DNA?
Phosphodiester bonds (covalent)
What are the 3 bonds that hold the 2 strands of DNA together?
- H- bonds (horizontal)
- Hydrophobic interactions (vertical)
- Na+ neutralise O- on acidic phosphates on outside of molecule (2 strands can associate)
How is a phosphodiester bond formed?
By the elimination of the 3’-Carbon hydrogen + of hydroxyl group from the 5’ end.
What are the 4 stages of Agarose gel electrophoresis?
- Gel is cast
- Buffer is Tris-acetate-EDTA
- DNA samples are loaded in a dye mix of polymer / buffer / BPB
- Nucleic acid migrate to + anode.
In agarose gel electrophoresis which side is the DNA added to?
Cathode (-) (DNA has a net negative charge)
In agarose gel electrophoresis what part of the dye (Gel-Red) allows it to bind to nucleic acid?
The positive charge on the nitrogen of Gel-Red binds to the negatively charged phosphates of nucleic acids
