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Higher Biology Unit 1: 1.1 Structure of DNA
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Starter Make a mind map of the key points you remember about DNA from Nat 5 biology in your jotter
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Learning Intentions Name the molecules in a DNA nucleotide and identify them in a diagram Name the type of bond on the backbone of the DNA molecule Give the names of the 4 DNA bases Describe the base pairing rule for DNA bases
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Deoxyribonucleic acid
The DNA molecule is comprised of two chains of nucleotides. The nucleotides are comprised of deoxyribose sugar, a phosphate and a base.
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DNA stands for Deoxyribose Nucleic Acid.
It is as double stranded molecule made up of subunits called nucleotides. Each nucleotide is made of 3 parts;- A base, a phosphate and a deoxyribose sugar.
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Nucleotides bond together to form a sugar-phosphate backbone
Nucleotides bond together to form a sugar-phosphate backbone. This is due to chemical bonds between the phosphate group of one nucleotide and the carbon 3 of the deoxyribose on another nucleotide.
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This is what a nucleotide looks like at the molecular level…
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Nucleotides bond together to form a sugar-phosphate backbone
Nucleotides bond together to form a sugar-phosphate backbone. This is due to chemical bonds between the phosphate group of one nucleotide and the carbon 3 of the deoxyribose on the next nucleotide. The double helix is described as having two anti-parallel chains of nucleotides because one side goes from 5’ to 3’ (five prime to three prime) and the opposite side goes from 3’ to 5’.
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The Code There are 4 different types of base in DNA. Thymine = T
Adenine = A Guanine = G Cytosine = C They have complementary base pairing T pairs with A G pairs with C
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The bases pair up using hydrogen bonds to form the double helix shape.
C and G 3 bonds T and A 2 bonds
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These bases are described as being complementary to each other
These bases are described as being complementary to each other. This means their shapes match up.
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