[IB SYLLABUS]
Label and annotate the structure of a single nucleotide
Label and annotate the structure of a single nucleotide
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| copyright KSJ |
DNA is a double helix,
it has two strands that twist around each other. Each of these strands is known
as a nucleotide(see left). Nucleotides are made of phosphate, deoxyribose
sugar, and a base.
Phosphate
•
Acidic
•
Negatively charged
Deoxyribose
sugar
•
5 carbon atoms= pentose sugar
•
If the sugar is deoxyribose, the polymer is DNA
•
If the sugar is ribose, the polymer is RNA
Base
•
Contains nitrogen
•
Has one or two rings in its structure
State the type of
bond that joins A to B and A to C
Covalent bonds
Write down which
bases pair with each other(complementary base pairs)
There are four possible
bases: cytosine, guanine, adenine, and thymine. Cytosine always pairs with
guanine and adenine always pairs with thymine. To easily remember this, just
remember the acronym 'AT' which stands for adenine and thymine. If we know
this, then we can assume that guanine and cytosine are the other pair.
Distinguish between DNA and RNA
Draw a section of
DNA, showing two anti-parallel strands if four nucleotides each. Label the
bonds which hold the bases together as well as the correct complementary base
pairs
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| Copyright PoS |
Two benefits of
modeling rather than an experimental approach
• Allows people to visualize the molecule
• Lets people see how well it fits with the
available evidence
Outline the reasons
the first model was rejected
• Ratio of adenine to thymine was not 1:1
• Required too much magnesium
Two key discoveries
concerning of DNA that were found quickly after the model was published
• DNA must be a double helix
• Strands must be anti-parallel to allow base
pairings to happen
Give an example of
the work of other scientists that supported Watson and Crick's discovery
• Rosalind Franklin and Maurice Wilkins, who
used X-ray diffraction
PoS
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