Chapter 12: Molecular Genetics

1. Chapter 12: Molecular Genetics DNA structure Replication Protein synthesis

2. DNA: The Genetic Material Section 1 – p. 329

3. The “OLD” people of DNA • Fredrick Griffith • Oswald Avery • Hershey and Chase • Erwin Chargaff • Watson and Crick

4. Fredrick Griffith-1928 • In 1928, British scientist Fredrick Griffith was trying to learn how certain types of bacteria caused pneumonia. • He isolated two different strains of pneumonia bacteria from mice and grew them in his lab. • Performed the first major experiment that led to the discovery of DNA as the genetic material

5. So Griffith, Avery, Hershey and Chase all helped discover DNA and the importance that it plays in transferring Genes. But what is DNA??? what is it made of??? what does it look like??????

6. What is DNA? A genetic code A molecule made of subunits called nucleotides A complex molecule that is arranged as a double helix.

7. NUCLEOTIDES are repeating subunits (monomers) that include: Phosphate group 5-Carbon sugar Nitrogen base

8. NUCLEOTIDES the smallest subunit of DNA

9. Two Kinds of bases in DNA • Pyrimidinesare single ring bases. • Thymine & Cytosine • Purines are double ring bases. • Adenine & Guanine Memory trick “Y” are you single?

10. A G C T

11. Erwin Chargraff- • Analyzed the amounts of A, C, T, and G in DNA; Discovered A=T & C=G

12. The Shape of DNA • DNA often is compared to a twisted ladder. • Rails of the ladder are represented by the alternating deoxyribose and phosphate. • The pairs of bases (cytosine–guanine or thymine–adenine) form the steps.

13. Watson and Crick • Built a model of the double helix that conformed to the others’ research • 1. two outside strands consist of alternating deoxyribose and phosphate • 2. cytosine and guanine bases pair to each other by three hydrogen bonds • 3. thymine and adenine bases pair to each other by two hydrogen bonds

14. Watson and Crick • suggested the structure for DNA and Hypothesized a method of replication

15. Refer to the DNA handout • Locate the Phosphate groups (small circles). Label each one with “P” • Color all phosphate groups orange • Locate the deoxyribose sugar molecules (large pentagon shapes attached to the P’s). Label them by name. • Color all sugars blue

16. Refer to the DNA handout • Locate the nitrogen bases. Label the first base by name and the others “NB”. • What do you notice about these molecules?

17. 4 Nitrogen Bases

18. Refer to the DNA handout • Locate the nitrogen bases – 2 large, 2 small • Label one of the large bases Adenine • Label the other large base Guanine • Label one of the smaller bases Thymine • Label the other small base Cytosine • Color each base a different color.

19. CHARGAFF’S BASEPAIRING RULES A binds with T G binds with C

20. Hydrogen Bonds

21. 3-D Animation of DNA http://www.umass.edu/molvis/tutorials/dna/dnapairs.htm

22. Stop & Review • What is the smallest subunit of DNA? • List 3 parts to #1? • What are the side chains of DNA made of? • What are the “steps” of DNA made of? • What are the base pairing rules of DNA? • Describe the structure of DNA in 2 words.

23. ANSWERS • Nucleotide • Sugar, phosphate and a nitrogen base • Sugar and phosphate • Nitrogen base • A=T, C=G • Double Helix

24. How are genes, chromosomes and DNA related? Genes are portions of DNA that are tightly packed into chromosomes and code for the manufacture of proteins.

25. How are genes, chromosomes and DNA related? Think of chromosomes as socks and genes as stripes on the socks.

26. Place in order from smallest to largest. Gene DNA Chromosomes

28. Have Your DNA & eat it too! • Collect materials • Follow instructions *A (pink) pairs with T (green) *C (orange) pairs with G (yellow)

29. Semi-conservative replication Part 2

30. Essential Questions What is replication and how is it done? What’s the role of the enzymes helicase and DNA polymerase?

31. Replication • A complete copy of the DNA is made The DNA code is in the middle of the helix, so how does it get copied if it’s obscured by the side chains and twist of the helix shape?

32. Replication • DNA replication is an important part of the cell division process. • Before a cell divides, it first duplicates its DNA so that the new cell will have the same genetic information. • The specific base pair matching during replication ensures that exact DNA copies are made.

33. The DNA code is in the middle of the helix, so how does it get copied if it’s obscured by the side chains and twist of the helix shape?

34. Replication Replication • Enzymes (helicase) will “unzip” or unwind the double helix by weakening H-bonds creating a replication fork where the two chains separate • DNA polymerase assembles new DNA using each original strand as a template • The replicated DNA is proofread and mistakes are edited

35. Replicationfork

36. Boring person explaining 

37. Replication is discontinuous • Short fragments of DNA called Okazaki fragments are added near the replication fork • Then gaps are filled in by DNA polymerase • Bases are added following the base pairing rules (A-T, C-G) * The lengths of Okazaki fragments are between 1,000 to 2,000 nucleotides long in bacteria and are generally between 100 to 200 nucleotides long in eukaryotes.

38. Copy the following sequence to your foldable. T-- A-- C-- A-- A-- A-- C-- T-- T-- A-- C-- T-- --A --T --G --T --T --T --G --A --A --T --G --A Remember that H-bonds hold complementary bases together

39. Unzip sequence to your foldable. Step 1: Helicaseenzyme “unzips” double helix by weakening H-bonds T A C A A A C T T A C T A T G T T T G A A T G A

40. Using the original DNA sequence on the foldable make a copy. Step 2: DNA polymerase enzyme adds DNA bases to the exposed nucleotides on the leading strand A T G T T T G A A T G A T A C A A A C T T A C T A T G T T T G A A T G A

41. Using the original DNA sequence on the foldable make a copy. While Okazaki fragments are added on the lagging strand A T G T T T G A A T G A A C A A C A C T T A C A A A C T T A C T A T G T T T G A A T G A

42. Using the original DNA sequence on the foldable make a copy. Step 3: Polymerase also proofreads and edits any gaps A T G T T T G A A T G A T A C A A A C T T A C T T A C A A A C T T A C T A T G T T T G A A T G A

43. RESULTS • TWO strands of identical DNA • DNA replication is known as semiconservative meaning each DNA molecule contained one original strand an one new strand.

45. Have Your DNA & eat it too! • Now replicate the DNA, using 2 more pieces of licorice but use black sticks

46. 3-2-1 3 steps cells undergo in replication 2 words meaning the structure of DNA 1 word for duplicating cell DNA

47. Protein synthesis Part 3

48. Warm-Up Quiz: DNA 101 • DNA is a double stranded sequence of ___________ (smallest unit of DNA). • DNA is a code of instructions for building ___________ (molecule). • DNA is stored in the _________ (control center of the cell). • The DNA code must be transmitted to the ___________ where proteins are built. Today we’ll see how this happens.

49. Essential Questions • What is the primary function of DNA? • How do RNA and DNA compare? • What are the three main types of RNA? What are their roles? • How do the base-pairing rules for RNA compare to the rules for DNA? • Describe the roles of DNA and RNA in the overall process of protein synthesis.

50. The role of DNA is to store and transmit genetic information