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Chapter 21

Chapter 21. DNA and Biotechnology. DNA Is a Double Helix Consisting of Two Strings of Nucleotides. During Replication of DNA Each Original Strand Serves As a Template for a New Strand. DNA Replication. DNA Replication. Process: DNA strands uncoil and “unzip”

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Chapter 21

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  1. Chapter 21 DNA and Biotechnology

  2. DNA Is a Double Helix Consisting of Two Strings of Nucleotides

  3. During Replication of DNA Each Original Strand Serves As a Template for a New Strand

  4. DNA Replication

  5. DNA Replication • Process: • DNA strands uncoil and “unzip” • DNA nucleotides are positioned and linked by DNA polymerase • Nucleotide subunits: A = adenine, G = guanine, T = thymine, C = cytosine • A only binds to T; and G only binds to C

  6. DNA Codes for RNA, Which Codes for a Protein • Central Dogma DNA  RNA  Protein

  7. Central Dogma

  8. Which of the following statements about DNA and RNA is/are incorrect? • DNA is double stranded, RNA single • DNA contains deoxyribose, RNA ribose • DNA contains four bases A, T, G, C, RNA only contain three, A, G, C • DNA forms a double helix, RNA doesn’t

  9. RNA Transcription

  10. RNA Synthesis: Transcription • Process: • DNA for a gene unwinds • RNA polymerase copies base sequence in RNA nucleotides • Ex.: G-C-T-A  C-G-A-U (note U instead of T)

  11. Transcription of a Gene into mRNA

  12. Which RNA nucleotide sequence (mRNA) would the DNA sequence (T-A-C-G-C-T) specify? • A-T-G-C-G-A • A-U-G-C-G-A • T-A-C-G-C-T

  13. Genetic Code • Codon: sequence of three mRNA bases that codes for an amino acid • Duplicate codons: almost all amino acids have more than one codon (degenerate code) • Genetic Code Grammar • Start: AUG (methionine), begin all genes • Stop: UAA, UAG, UGA, one ends each gene

  14. Which amino acids (protein) would the DNA sequence (T-A-C-G-C-T) code for? • Val-Ala • Phenal-Isoleu • Isoleu-Gly • Gly-Asp • Met-Arg

  15. Protein Synthesis: Translation • Components: messenger RNA, transfer RNA, ribosomes of ribosomal RNA and proteins • Process: • Initiation: tRNA finds start (AUG) codon, binds ribosome and mRNA • Elongation: tRNA brings specific amino acids to developing protein chain • Termination: stop codon terminates developing chain, protein is released from ribosome

  16. Three Steps of Translation

  17. Point mutations Result from nucleotide insertion, substitution, or deletion Replacement of nucleotide in DNA may (or may not) lead to a change of amino acid in protein DNA Mutations

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