Structure

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Chapter 8

• Structure Function of Genetic Material

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Terminology

• Genetics
• Genome
• Chromosome
• Gene
• Locus
• Alleles
• Genotype/Phenotype
• Heredity

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The single chromosome of E. coli
4.6 million base pairs
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• There are two types of nucleic acids
• deoxyribonucleic acid (DNA)
• ribonucleic acid (RNA)
• enable living organisms to reproduce complex
  components from one generation to the next
• DNA provides directions for
• its own replication
• RNA synthesis
• controls protein synthesis

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Nucleic Acids are composed of chains of
nucleotides
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DNA

• Polymer of nucleotides
• Sugar-phosphate backbone"
• covalent bonds
• Hydrogen bonds between complementary bases
• AT and CG
• antiparallel
• semi-conservative replication

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ADDING NUCLEOTIDE TO DNA
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• Genes - linear sequence of DNA nucleotides
• sequence of bases is unique for each gene
• hundreds to thousands of nucleotides long
• limitless number of possible base sequences
• Linear order of bases specifies amino acid
  sequence
• the primary structure of a protein
• specifies that proteins three-dimensional
  conformation

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Gene Expression
Central Dogma of Biology
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DNA Replication

• Formation of the replication fork
• begins at a specific location on the circular
  bacterial chromosome and proceeds in both
  directions
• enzymes break hydrogen bonds between bases
• DNA Polymerase directs synthesis of new DNA
  strands complementary to the original strands
• Adds nucleotides to the 3 end of the new strand
• leading strand
• DNA polymerase must jump forward and work
  backward on 5 strand
• lagging strand composed of Okazaki fragments
  joined by ligase

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• Carbons of sugar are numbered
• At 3' end, a hydroxyl group is attached to the 3'
  carbon of the terminal sugar
• The 5' end terminates with the phosphate group
• New nucleotides are added to the 3' end of the
  growing strand
• New strands are synthesized in 5' to 3' direction

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DNA Replication
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• Enzymes involved in DNA replication
• DNA Gyrase
• Helicase
• Primase
• DNA Polymerase III
• DNA Polymerase I
• DNA ligase

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• Step 1. Unwinding reduction of tension
• Step 2. Initiation
• This occurs simultaneously on both template
  strands
• Step 3. Elongation
• Continuous on the leading strand
• Discontinuous on lagging strand producing Okazaki
  fragments
• Step 4. remove RNA primer and fill gap with DNA
• Step 5. seal the backbone of the lagging strand
• Step 6. proofread during elongation
• Mismatch bases are removed and replaced with the
  appropriate base

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