Biology 1202B Lecture Notes - Nucleoid, Interphase, Semiconservative Replication

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30 Apr 2012
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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
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