Molecular Genetics - Molecular Genetics A Structure of DNA...

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Molecular Genetics A. Structure of DNA 1. Nucleotides- monomer for DNA a. pentose sugar- deoxyribose b. phosphate group c. nitrogenous bases - pyrimidines- thymine, cytosine - purines- adenine, guanine 2. 3’, 5’ phosphodiester linkage- a phosphate can link onto the 3’ or 5’ carbon on the pentose sugar a. polynucleotide chain- many nucleotides linked. 1 end must be 5’ the opposite must be 3’ 3. Base pairing a. bases form hydrogen bonds b. Adenine – Thymine c. Cytocine – Guanine
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4. DNA molecule
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a. two polynucleotide chains b. coiled double helix c. complementary- the sequence of bases in one strand dictates the sequence of bases in the opposite strand. d. antiparallel- the strands run in opposite directions. Must do this to correctly orient bases for it to bond B. DNA Replication 1. Semiconservative 2. Origin of Replication a. Unwinding- DNA forms a bubble in the middle of strands and as the bubbles move the DNA unwinds; breaking Hydrogen bonds. - DNA helicase enzymes- responsible for unwinding - helix destabilizing proteins- hold strands steady while new DNA is added 3. DNA synthesis a. DNA polymerases- makes new DNA, adds nucleoside Triphosphate - proofreads - two extra phosphates break off for the Energy necessary to bring the base in for bonding 4. RNA Primer- starts on the 3’ end of an existing polynucleotide a. after the new DNA is made, Primer is degraded and replaced by bases
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5. Discontinuous/ continuous a. replication fork b. leading strand- DNA is synthesized toward fork, continuous c. lagging strand- DNA is synthesized away from fork, discontinuously: in fragments of 100-1000 nucleotides - Okasaki fragments d. DNA ligase- pieces Okasaki fragments together
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6. Bidirectional
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Molecular Genetics - Molecular Genetics A Structure of DNA...

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