2. DNA, Genes, and Gene Expression Grades 9-12 M. Wetherbee

3. Secret of Life Watson and Crick – Structure Roslin Franklin and Maurice Wilkens – X-ray diffraction Erwin Chargaff – Chargaff’s rules

4. DNA Structure Deoxyribonucleic acid DNA is a chain of nucleotides – Each nucleotide is composed of: Phosphoric acid A pentose sugar (deoxyribose) A nitrogen-containing base

5. Nucleotides: Chargaff’s Rules Still Apply Chemically: – Adenine (A) always pairs with thymine (T) – Cytosine (C) always pairs with guanine (G) Purines – Adenine and guanine Pyrimidines – Thymine and cytosine So if A always pairs with T, and C with G, what is the complementary code for TTACGATGGC?

6. The Spiral Staircase Double helix Nucleotides held together with hydrogen bonds Sugar-phosphate backbone held together covalently

8. 20 Billion Miles In a typical human cell there is about 6 ½ feet of DNA That means that in the entire human body, there are up to 20 billion miles of DNA! How does a cell store nearly 7 feet of DNA?

10. Structure Provides Means of Replication “It has not escaped our notice that the specific pairing we have postulated immediately suggests a possible copying mechanism for the genetic material.”

11. RNA DNA – Double-stranded – Deoxyribose sugar – Thymine RNA – Single- stranded – Ribose sugar – Uracil

12. DNA Replication DNA helicase ‘unzips’ the two strands DNA polymerase lays down new bases Identical strands

13. Gene Expression DNA is read like a blueprint to make something the cell needs – Usually proteins Transcription Translation

14. Transcription and Translation Transcription – Segment of DNA serves as template for RNA molecule Translation – mRNA provides directions for synthesis of a protein by a ribosome http://www.youtube.com/watch?v=41_Ne5m S2ls http://www.youtube.com/watch?v=41_Ne5m S2ls