• 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) © Pearson Education Ltd 2008 This document may have been altered from the original
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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)
© Pearson Education Ltd 2008This document may have been altered from the original
Genetic jargon
• DeoxyriboNucleic acid • Contain instructions on how to build
proteins used in the body.• Found in cell nucleus.• Codes for individual Proteins.
DNA
A double helix
© Pearson Education Ltd 2008This document may have been altered from the original
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
Mononucleotides or nucleotides
• Monomers of Nucleic acids
• Each nucleotide is made of
-Phosphate group
-Pentose sugar
-Nitrogenous base
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
Ribose sugars in DNA and RNA
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
Organic bases are purines or pyrimidines
• Adenine and Guanine are purines
• Thymine, Uracil and Cytosine are pyrimidines
Part of a DNA part molecule
© Pearson Education Ltd 2008This document may have been altered from the original
PBASE
Sugar
PBASE
Sugar
PBASE
Sugar
PBASE
Sugar
DNA
PBASE
Sugar
Adenine
Guanine
Cytosine
Thymine
BASE
BASE
Thymine
Adenine
Thymine
BASE
Cytosine
BASEGuanine
BASEAdenine
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
© Pearson Education Ltd 2008This document may have been altered from the original
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
DNA replication
© Pearson Education Ltd 2008This document may have been altered from the original
Why semi conservative?
• A new double helix consists on I parent stand and 1 new strand
• Only one of the original strands is conserved
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