1. Unravelling DNA

2. DNA structure function packaging replication
Deoxyribonucleic acid-the chemical of life.
Click on an area below to find out more about DNA
structure
function
packaging
replication

3. structure In the form of a double helix structure.
Made up of a sugar-phosphate back bone and four types of nitrogen bases.
The four nitrogen bases are adenine (A), guanine (G), cytosine (C) and thymine (T).
The sugar-phosphate- nitrogen base unit is referred to as a nucleotide.

4. packaging
Human DNA is up to 1m in length (ie. 3 million base pairs in length). Yet we have 46 molecules within the nucleus of our body cells.
DNA is tightly wound up into structures we call chromosomes.
DNA coils around histone proteins. 8 ball-shaped histone proteins and DNA forms a nucleosome.
DNA molecule
Histone proteins
Pair of sister chromatids, the DNA molecule has replicated in preparation for cell division.
For more on how DNA copies itself see the replication section.
Chromosomes are a package of DNA and protein called chromatin.

5. function DNA is ubiquitous to life.
Sections of DNA are known to code for the manufacture of proteins.
These sections are called genes.
Proteins are a diverse group of organic substances that essentially make up living organisms.
Hence DNA contains instructions for making a living organism, whether it be a bacteria, flea, elephant or human.
function
The characteristics of an organism, as determined by the genes, can also be passed on from one generation to the next.
Hence DNA is also the vehicle for inheritance of characteristics.
Gene for skin pigment, eg melanin production
Gene for lactose production
chromosome

6. For cells to divide into new cells and still contain all the necessary instructions (genes), DNA must have the ability to replicate itself.
DNA replication is said to be semi-conservative as each new DNA molecule contains one strand from the original and one newly synthesised strand.
replication
DNA replicates with the help of enzymes (DNA helicase, DNA polymerase and DNA ligase).
After DNA unwinds and unzips, DNA polymerase adds free nucleotides to each strand (base pair rule).
One strand is created continuously while the other needs to be created in segments due to the 5΄ and 3΄ polarity of DNA