DNA is the blueprint of life found in the nucleus of cells. It was discovered in 1953 by Watson and Crick to have a double helix structure. DNA can be extracted from cells like those found in kiwi fruit through a process of breaking down the cell and nucleus membranes, filtering out the DNA-containing solution from cell debris, and using alcohol to precipitate out the DNA. The salt in the extraction solution stabilizes the DNA while the detergent breaks the cell membrane, releasing the cell contents, and filtering removes insoluble parts to leave DNA, RNA, and amino acids, with DNA then being isolated through its insolubility in alcohol.

1. DNA: deoxyribonucleic acid
DNA is packed in nucleus of cells
It looks like a double-helix
found by Watson and Crick in 1953
DNA is the blueprint of life
Interesting facts!
One DNA molecule in a human cell is 1 meter long while
diameter of the cell’s nucleus is 1/10^5 meter
A-T; G-C in a double-helix DNA, so if the sequence of one strand
is known, we can find the sequence of the other
Extraction DNA from kiwi fruits
All living things, including kiwi
fruit, are made up of cells.
Step 1: Break down cell
membrane and nucleus
membrane
Step 2: Filter solution
containing DNA out of cell
debris
Step 3: Precipitation DNA
out of the solution
Nucleus membrane
Cell organells
Nucleus Cell membrane
Nucleu
s
Lysis solution made of
washing up liquid and salt
Filter by coffee filter paper
Ice-cold 95% alcohol

2. So…how exactly does it work? All living things, including kiwi
The salt stabilises the DNA so it does not break down
when you extract it. It does this by providing positive
charge to neutralise the natural negative charge of
DNA.
The cell membrane is essentially a lipid (fat) bilayer
(2 layers). The washing up liquid breaks this bilayer
into small fat droplets. When this happens the cell
contents are released.
All the insoluble parts of the fruit (cell walls etc.)
are removed so we are left only with the cell
contents, i.e. mainly DNA, amino acids and RNA.
Remember it is the DNA we are interested in.
DNA is soluble in water, but not in alcohol. When
alcohol is added, the DNA molecule becomes
insoluble and precipitates out of the solution,
becoming visible as a white stringy solid, between
the alcohol (less dense) and water (more dense)
layers.
fruit, are made up of cells.
Step 1: Break down cell
membrane and nucleus
membrane
Step 2: Filter solution
containing DNA out of cell
debris
Step 3: Precipitation DNA
out of the solution
Nucleus membrane
Cell organells
Nucleus Cell membrane
Nucleu
s
Lysis solution made of
washing up liquid and salt
Filter by coffee filter paper
Ice-cold 95% alcohol