Core: DNA
- Created by: jross10
- Created on: 30-03-15 12:46
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- DNA
- A double helix of paired bases
- DNA molecule has two strands coiled together in shape of double helix (two spirals)
- Two strands held together by chemicals called bases
- Four different bases: Adenine (A); Cytosine (C); Guanine (G); Thymine (T)
- Bases are paired (always in the same way): A-T; C-G; called base-pairing
- Base pairs joined together by weak hydrogen bonds
- Gene is a section of DNA and the sequence of bases in a gene code for a specific protein
- Watson, Crick, Franklin and Wilkins discovered DNA Structure
- Rosalind Franklin and Maurice Wilkins
- Discovered helical structure by directing beams of x-rays onto crystallised DNA and looking at patterns formed
- James Watson and Francis Crick
- Used structure along with knowledge that Adenine and Guanine matched amount of Thymine and Cytosine to make model of DNA molecule
- Rosalind Franklin and Maurice Wilkins
- Practical to extract DNA
- 1 - chop some onion and place in a solution of detergent and salt
- detergent breaks down cell membranes and salt makes DNA stick togetehr
- 2 - put beaker into water bath of 60 for 15minutes
- denatures enzymes that could digest DNA and softens onion cells
- 3 - put beaker in ice to cool
- stops DNA from breaking down
- 4 - once mixture is ice cold put into a blender for a few seconds
- breaks down cell walls and releases DNA
- 5 - cool mixture again then filter to get froth and big bits of cells out
- gently add ice cold alcohol to mixture
- DNA starts coming out; appears as stringy white substance
- 1 - chop some onion and place in a solution of detergent and salt
- A double helix of paired bases
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