nucleic acids
TRANSCRIPT
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• Describe the basic structure of a mono-nucleotide and how they bond to form DNA (include complementary base pairing) and RNA
• Explain the nature of the genetic code (triplet code only; non-overlapping and degenerate not required at AS)
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Genetic jargon
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• DeoxyriboNucleic acid • Contain instructions on how to build
proteins used in the body.• Found in cell nucleus.• Codes for individual Proteins.
DNA
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A double helix
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2 forms of Nucleic acid
• DNA – deoxyribonucleic acid
found in nucleus
• RNA – ribonucleic acid
found in 3 different forms
• Hold coded information to build an organism
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Mononucleotides or nucleotides
• Monomers of Nucleic acids
• Each nucleotide is made of
-Phosphate group
-Pentose sugar
-Nitrogenous base
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What are the differences between DNA and RNA?
• DNA – pentose sugar - deoxyribose• Nitrogenous base DNA – Four types:• Double strand RNA –Pentose sugar - ribose A C G and Uracil instead of Single strand
A
C G
T
T
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Ribose sugars in DNA and RNA
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Joining Nucleotides together
• Condensation reaction between
• Phosphate of one nucleotide and sugar of another
• Phosphodiester Bond• Backbone of chain =
sugar- phosphate • Bases project into
centre
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Organic bases are purines or pyrimidines
• Adenine and Guanine are purines
• Thymine, Uracil and Cytosine are pyrimidines
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Part of a DNA part molecule
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PBASE
Sugar
PBASE
Sugar
PBASE
Sugar
PBASE
Sugar
DNA
PBASE
Sugar
Adenine
Guanine
Cytosine
Thymine
BASE
BASE
Thymine
Adenine
Thymine
BASE
Cytosine
BASEGuanine
BASEAdenine
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Hydrogen bonding and base pairing
A-T, C-G and number of hydrogen bonds • Chains are the same distance apart
• Because base pair up in a particular way
• Pyrimidine pairs up with a purine
• A with T or U
• C with G
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DNA Replication
• The double helix is untwisted• Hydrogen bonds between the bases are
broken apart to unzip the DNA• Bases are exposed• Free nucleotides are H bonded onto the
exposed bases• Covalent bonds formed between
phosphate and sugar to make the backbone
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DNA replication
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Why semi conservative?
• A new double helix consists on I parent stand and 1 new strand
• Only one of the original strands is conserved