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2012.02.13 - Bio 1202 Lecture Review Notes.docx

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Biology 1202B
Gardiner/ Murphy

Biology Lecture Review Notes Lecture 1 History of DNA  1952 – Hershey and Chase – used to believe protein was inherited, but realized it was DNA  1953 – Watson, Crick and Franklin – discovered the double helix structure of DNA o Rosalind Franklin used X-ray diffraction on a DNA sample, which revealed positions of the atoms in the crystal (resembled the helical structure)  She died in her 30s from cancer (most likely from radiation due to her research), and she did not win the Nobel prize because she was dead (Watson and Crick won it for using her research to “discover” the helix structure)  1956 – Tijo and Levan – discovered there were 46 chromosomes in the nucleus  1963 – Margit and Sylvan Nass – discovered mtDNA (mitochondrial DNA) Structure of DNA/RNA  Nucleotides are the building blocks of nucleic acid (DNA and RNA) o Consist of a phosphate group, a pentose sugar and a nitrogenous base  Triphosphate – consists of 3 phosphates  Deoxyribose sugar – the pentose sugar in DNA, which is missing an oxygen atom  Ribose sugar – the pentose sugar in RNA, which has the oxygen atom  Nitrogenous Bases: o Guanine (G) o Adenine (A) o Thymine (T) – not in RNA o Uracil (U) – not in DNA o Cytosine (C)  DNA and RNA are made up of dNTP (deoxynucleoside triphosphate) o Examples: dATP, dCTP, dGTP, dTTP, and dUTP  Differences between RNA and DNA: o Ribose sugar  The C2 position in DNA does not have an OH group, which makes it more stable  The C2 position in RNA has the OH group, which makes it less stable o Nitrogenous bases  DNA has thymidine, which has a methyl group  RNA has uracil, which does not have a methyl group o Strand  DNA is double stranded  RNA is single stranded  Nucleotide = Nucleoside + Phosphate o Examples of nucleosides: deoxyadenosine, deoxyguanosine, deoxythymidine, deoxyuridine, and deoxycytidine o Nucleoside = Sugar + Base o Nucleotide = Sugar + Base + Phosphate  Sugar phosphate backbone – the structure of the 5’ to 3’ with bases off to the right side o 5’ end – has a phosphate group o 3’ end – has a hydroxyl (OH) group o Phosphate bridges – 3’ carbon to 5’ carbon from two different sugars  Called a 3’ to 5’ phosphodiester bond  Bases are fused rings of carbon and nitrogen o Purines – double-ring structures  Includes adenine (A) and guanine (G) o Pyrimidines – single-ring structure  Includes thymine (T) and cytosine (C)  Double helix structure: o There is hydrogen bonding between the base pairs in a double helix o The two ends are anti-parallel  One strand is 3’ at the bottom, and the other is 5’ at the bottom o A always binds to T (with 2 hydrogen bonds) o C always binds to G (with 3 hydrogen bonds)  It is not physically possible for two purines to bond (too large to fit)  It is not physically possible for two pyrimdines to bond (too small to fit) o Distance between each pair of bases = 0.34nm
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