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5/10/12 Lecture 1 DNA is the genetic material Chemical composition of DNA




FRED GRIFFITH

Investigated streptococcus pneumonia ( in mice )
Two types
Rough ( rippled)
Smooth ( shiny bigger colony ­ made by polysaccharide capsule that coats colony ­shininess)
Smooth ­ pathogenic in mice
Rough ­ non-pathogenic
Smooth ­…

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isolated DNA. This was the agent that could produce an enduring, heritable change in an organism


HERSHEY & CHASE

Bacteria: Escherichia coli
Phage T2 ­ virus of bacteria ( smaller than that, which infects eukaryotic cells )
Phage : protein + DNA
T2 infects E.coli
Phage replicates in infected E.coli…

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TYPES OF BASES: PURINES- nitrogen-containing heterocyclic compounds- TWO RINGED STRUCTURE



Amine




ADENINE 6-aminopurine GUANINE 2-amino-6-oxopurine

Pyrimidine ­ heterocyclic bases ­ ONE RINGED STRUCTURE




THYMINE-5-methyluracil CYTOSINE 2-oxo, 4-amino pyrimidine URACIL 2,4-dioxopyrimidine




When the phosphate is attached to the sugar-base compound its called a NUCLEOTIDE, if its only the
sugar and the…

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AMP -Adenosine monophosphate, or AMP, on its own, plays a role in signaling energy depletion in
cells, and in chemical combination forms a component of a number of cofactors

BASE Nucleotide
Adenine A Adenosine
Guanine G Guanosine
Cytosine C Cytidine
Thymine T Thymidine
Uracil U Uridine




Phosphateput in water (…

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The four common ribonucleotides of RNA

- adenylate,

- cytidylate,

- guanylate

- uridylate




LECTURE 2 the structure of DNA double helix, packaging cell properties of DNA

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Forces that determine macromolecule structure

1. Covalent bonds
Very strong- single and double
Short C-C = 1.54 Å
Shared electrons
85-175 kcal/mol



2. Non-covalent bonds
-electrostatic interactions


Depends on dielectric constant (resistance that is encountered when forming an electric field in a
medium)- aqueous solutions have a high dielectric constant…

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The phosphate must be on the outside

Pauling & Corey's unsatisfactory model 3 strands - phosphates on the inside

Bases come in pairs

Relative base composition A=T C=G E. Chargaff

Bases share the same dimension

X-ray diffraction of a DNA fibre ­ DNA is helical- B form of DNA R.…

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What are the physical and functional consequences of DNA supercoiling?
DNA and its constituent nucleotides have similar U.V. absorption spectra with a
maximum around 260 nm. However, the total nucleotides that make up DNA
absorb more strongly than the polymer, so hydrolysis of DNA is accompanied
by a considerable increase…

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THE CENTRALO DOGMA ----
---- DNA--- CODES---RNA--- CODES--- protein


What are proteins
Polymers of amino acids
Allow enzymes to have wide diversity
Complex 3-d dimension
Structural and functional


What are enzymes
Proteins that catalyse biochemical reactions
Need enzyme to make covalent bond in protein


Enzymes that manipulate DNA
nucleases
ligases…

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recognise 'palindromes' because they bind to DNA as dimers (any molecular structure of any size in
which two initially identical chemical entities have become covalently combined)




Render its DNA immune to the action of its own restriction enzyme(s)




DNA fragments with the same sticky ends can be ligated together (anneal)…

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