DNA and Replication


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DNA and Replication

  1. 1. DNA and RNAChapter 12
  2. 2. Structure of DNA Deoxyribose sugar Phosphate Nitrogen Containing Bases – Adenine – Cytosine – Guanine – Thymine
  3. 3. DNA Nucleotides(Figure 12-5) Purines Pyrimidines Adenine Guanine Cytosine Thymine Phosphate group Deoxyribose
  4. 4. Structure of DNAFigure 12-7 Nucleotide Hydrogen bonds Sugar- phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G)
  5. 5. DNA ReplicationGenetic information is duplicatedMust be done before cell division cantake place Nucleotide Hydroge n bonds Sugar- phosphate backbone
  6. 6. DNA Replication S phase of mitosis Prokaryotes – Begins at a single point and proceeds until chromosome is replicated Eukaryotes- occurs at hundreds of places – Proceeds in both directions – Replication forks
  7. 7. 1 Phosphate + 1 Nucleotide = 1 Deoxyribose sugar + 1 Nitrogen Base Deoxyribose is a 5 carbon sugar. Chemists number each carbon according to its position in the sugar. The numbering system is used when describing DNA Replication
  8. 8.  The arrangement of the nucleotide is ALWAYS the same: – The Nitrogen base binds at the 1’ position – The Phosphate group binds at the 5’ position The 3’ position is also important. The phosphate group of the next nucleotide binds at the 3’ carbon.So, each strand of the DNA molecule runs in a 5’ to 3’ direction (from one nucleotide to the next)
  9. 9. Let’s Simplify. . .  Remember that the strands are complimentary.  The top strand runs 5’3’ (LR) and the bottom strand runs 5’3’ (RL)
  10. 10. And now. . .DNA Replication 1. The Hydrogen bonds between the nitrogen bases are broken by DNA Helicase (enzyme)**you could say that DNA polymerase The original strands serve“unzips” the nitrogen bases and then as templates duringreattaches the new nucleotides replication; something to be copied from
  11. 11.  2. Then new strands form using the template and the pool of nucleotides floating in the nucleus Replication occurs in a 5’ to 3’ direction on a 3’ to 5’ template
  12. 12.  3. Final step: Proofread – DNA polymerase will then go back and check to make sure that the nucleotides are matched up correctly. – So, what does that mean??
  13. 13. Final Product When replication is complete, we end up with two identical DNA molecules Each molecule contains 1 original strand and 1 new strand
  14. 14. Let’s See It in Action!!!!!!! How nucleotides are added in DNA replicat Thinkwell’s DNA Replication
  15. 15. DNA Replication(Figure 12-11) Original strand DNA New strand polymerase Growth DNA polymerase GrowthReplication Replication Nitrogenousfork fork bases New strand Original strand