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BACTERIAL GENETICS DEOXYRIBONUCLEIC ACID Nucleiod A. No nuclear membrane B. No paired chromosomes C. No nucleolus D. Single molecule DNA (circular) STRUCTURE of DNA ( see figs. in text) Components of DNA A. 2- deoxyribose 1. 5 carbon (C) sugar 2. Lacks O on #2 carbon B. Phosphate group (PO 4 ) C. Nitrogen (N) bases 1. Pyrimidines a. Thymine b. Cytosine 2. Purines a. Adenine b. Guanine D. Nucleotides 1. Subunits (structural units) of DNA 2. Structure of a nucleotide ( see fig. in text) a. 2-deoxyribose b. Phosphate group on #5 C c. Nitrogen base on #1 C E. Arrangement of nucleotides 1. Nucleotides form two chains 2. Bonds (covalent) between nucleotides a. P on #5C of one nucleotide b. #3C on next nucleotide 3. Two chains combined in ladder-like arrangement a. “Sides” of ladder - sugar and phosphate b. “Rungs” of ladder - two nitrogen bases 4. Pairing of N bases is specific a. Adenine to thymine - 2 “weak” hydrogen (H) bonds b. Guanine to cytosine - 3 “weak” H bonds D. Antiparallel structure of DNA 1. Chains of nucleotides - opposite directions
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2. One side - 5’ to 3’ side 3. Opposite side - 3’ to 5’ side 4. Two sides twist double helix ( see fig. in text) GENETIC CODE IN DNA A. Sequence of nitrogen base pairs = genetic code B. Language of DNA - DNAese 1. Symbols (alphabet) in DNA a. A = T b. T = A c. C G d. G C 2. Form three letter words - triplets 3. Each triplet codes for one amino acid 4. 64 triplets 5. 20 amino acids form proteins C. Gene - genetic code for one protein DNA REPLICATION ( fig. pg. in text ) A. Enzymes (DNA polymerases, DNA ligases) B. Begins at replication fork C. Each strand acts as template D. New nucleotides combine with complementary nucleotides on each parent strand E. Semiconservative replication - each new DNA strand = I/2 original DNA & 1/2 “new” DNA F. DNA polymerase adds new nucleotides in 5’ 3’ direction G. Formation of one strand - continuous or leading strand 1. Nucleotides added on one at a time as replication fork opens (from 5’ to 3’ )
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