Blend (homogenise) sample with salt + distilled water to break cells apart from each other.
Sit in detergent for 5-10 minutes - Disrupt cell membrane
Add protease (+RNAse) to break down histones and separated DNA from proteins.
Filter and add ice cold ethanol at 45 degrees to form a layer.
Extract Dna (white precipitate) using a stick inbetween the solution and ethanol.
Nucleotides join together to form polynucleotides.
The nucleotides join up between the phosphate group of one nucleotide and the sugar of another via a condensation reaction. This forms a phosphodiester bond.
A phosphodiester bond consists of a phosphate group and 2 ester bonds.
The chain of sugars and phosphate is known as the sugar-phosphate backbone.
Polynucleotides can be broken down into nucleotides again by breaking the phosphodiester bonds (using hydrolysis reactions).
Two polynucleotide strands join together to form a double-helix.
Two DNA polynucleotide strands join together by hydrogen bonding between the bases. Each base can only join will one particular partner - this is called complementart base pairing.
Adenine always pairs with thymine (A - T) and cytosine always pairs with guanine (C - G)
Adenine and Guanine are both purines which always pair with pyrimidines
Cytosine and thymine are both pyrimidines which always pair with purines.
Two hydrogen bonds form between A and T, and three hydrogen bonds form between C and G.
Two antiparallel polynucleotide strands twist to form the DNA double-helix.
DNA copies itself before cell division so that each new cell has the full amount of DNA.