Chapter 12: DNA Structure and Replication

1. Chapter 12:DNA Structure and Replication

2. 12.1 What Do Genes Do and What Are they Made of? • A segment of DNA that brings about the transcription of a segment of RNA. Agene may contain regulatory sequences, information for the synthesis of one or more proteins, or sequences that bring about the production of RNA used at such sites as the ribosomes.

3. 13.2 Watson and Crick: The Double Helix • 1953 presented the world with the structure of DNA • Cambridge University England • Watson23 • Crick35 • How did they infer the structure of DNA • X-ray diffraction Rosalind Franklin • 1962– Nobel Prize

4. 13.3 The Components of DNA and Their Arrangement • 3 Components • Phosphate • Sugar Deoxyribose • Nitrogenouse base • Adenine, Guanine, Cytosine, and Thymine • These three components make up one nucleotide and many nucleotides make up a DNA molecule • Structure • Sugar and phosphates are linked together “sugar-phosphate backbone” • Nitrogenous bases link the sugar-phosphate backbone. • Nucleotide Pairing Rules • Adenine+ Thymine • Guanine + Cytosine

5. The Structure of DNA Gives Away the Secret of Replication • How is genetic information passed on? • Each strand serves as a template for the new strand • Adenine always pairs with Thymine • Cytosine always pairs with Guanine • Once the two strands separate new nucleotides are synthesized that are complementary of the old strand

6. The Structure of DNA Gives Away the Secret of Protein Synthesis • The order of a group of nucleotides is going to be specific for a protein • Analogy • DNA Book • Protein genes Sentences • Nucleotides letters

7. The Building Blocks of DNA Replication • Building Blocks Nucleotides • Each Nucleotide has its own base • DNA Replication • The two strands unwind  with the aid of an enzyme  Helicase • Newly synthesized nucleotides attach to the strand enzyme DNA polymerase • End product two double strands

8. DNA Replication: Something Old, Something New • Two Double strands were made • The copies are also known as sister chromatids • Each having one parental DNA strand

9. Editing Out Mistakes • DNA base pairing occurs millions of times within a given DNA strand • Error rate rate at which nucleotides are mismatched occurs one in every billion by the end of replication • During replication mistake are made every 100,000 base pairs • DNA polymerases fix the mistakes

10. 13.4 Mutations: Another Name for a Permanent Change in DNA Sequence • Mutation a permanent alteration of a DNA base sequence • Incorrect bases are paired T+C instead of T+A or G+C • The C will be replaced with an A in order to correct it but the correct base pair was G+C • A new base pair is added to the gene • Point mutation a mutation of a single base pair in the genome

11. Example of Mutations : Cancer • Cancer mutation in cells causes them to proliferate rapidly • Point mutation A substituted for a T • Alters a protein in the cell • The Protein continues through the cell cycle, causing them to multiply wildly http://www.youtube.com/watch?v=TvwgUvGIcJA

12. Heritable and Non-Heritable Mutations • Somatic Cells cells that do not become egg or sperm • Cancer • Germ-line cells the cells that do become egg and sperm • Huntingtons • Heritable

13. What Causes a Mutation? • Environmental • Chemicals in cigarettes • UV light • Links adjacent T’s together • Causes strands to break • Random Spontaneous events • Free radicals • http://www.youtube.com/watch?v=TVyrv47m2ck&NR=1

14. The Value of Mistakes: Evolutionary Adaptations • As we’ve seen mutations can have a negative effect. • Germ-line mutations is the means by which new genetic information is added to a species’ genome • The form of new alleles new variants • Interesting Article: www.jyi.org/news/nb.php?id=204