DNA and RNA

1. DNA and RNA Chapter 12

2. 12-1: DNA

3. DNA Structure • DNA is made up of monomers called nucleotides • each nucleotide is made up of three parts: 1. 5-carbon sugar (deoxyribose) 2. phosphate group 3. nitrogenous base • FOUR types of nitrogenous bases adenine (A) & guanine (G) – purines cytosine (C) & thymine (T) – pyrimidines

4. Nitrogenous bases • purines (A & G):two rings • pyrimidines(C & T): one ring

5. Chargaff’s Rules • # of A = # of T • # of G = # of C • # of purines = # of pyrimidines

6. DNA “double helix” • discovered by Watson & Crick • two strands are wound around each other like a spiral staircase or twisted ladder

7. DNA “double helix” • base pairing explains Chargaff’s Rules • A always bonds with T (“points”) – double bond • C always bonds with G (“curves”) – triple bond

8. So if you have one side of DNA that has these bases, • Cytosine (C) • Adenine (A) • Thymine (T) • Guanine (G) • Guanine (G) • Thymine (T) --(G) Guanine --(T) Thymine --(A) Adenine --(C) Cytosine --(C) Cytosine --(A) Adenine These bases will make the other side.

9. DNA Origami

10. Two types of FOLDS

11. Step 1 Cut the white border off the top, bottom, and sides of the template.

12. Step 2 Fold all solid lines going lengthwise down the page into “mountain folds”.

13. Step 3 Fold all dashed lines going lengthwise down the page into “valley folds”.

14. Check Yourself Your paper should look like this:

15. Step 4 Bring the two sides of the model together, similar to an “I” beam.

16. Step 5 Look for the words ‘front’ and ‘back’ at the top of your model. Hold the model with the ‘front’ side facing you.

17. Step 6 Fold the two sides of the DNA model so the ‘front’ side is flat.

18. Step 7 Crease each solid, horizontal line into a mountain fold (away from you).

19. Step 8 Flip the model to the ‘back’ side. Crease each solid diagonal line into a mountain fold (away from you).

20. Check Yourself Your model should look like this.

21. Step 9 Fold ALL of the creases together in the directions of the folds made in steps 7 and 8. Your model will fold up like an accordion. While you are folding, pinch the middle of the model to keep it together to make a cylindrical shape.

22. Step 9

23. Step 10 Release the model. You should be able to see the shape of a double helix.

24. Step 11 Straighten out the sides of the DNA model (the DNA “backbones”) to make them perpendicular to the creases in the middle.

25. You’re DONE! 

26. SOL Review • A scientists is researching the effect long-term exposure to sunlight has on cell reproduction. Which scenario extends the current understanding of this relationship? • A) a culture of liver cells exposed to different pH levels over a 10-day period • B) a culture of muscle cells exposed to different nutrients over a 30-day period • C) a culture of skin cells exposed to different temperatures over a 50-day period • D) a culture of brain cells exposed to different electrical impulses over a 75-day period

27. 12-2: Chromosomes and DNA Replication

28. DNA and Chromosomes • prokaryotes have a SINGLE, circular chromosome in the cytoplasm containing their DNA

29. DNA and Chromosomes • prokaryotes have a SINGLE, circular chromosome in the cytoplasm containing their DNA • eukaryotes have MANY chromosomes in the nucleus containing their DNA

30. Chromosome Structure • DNA is very tightly packed • DNA is wound around histones (proteins) to form nucleosomes • nucleosomes wind into coils and supercoils to ultimately form chromosomes tightly wound DNA is called chromatids

31. Flashback! What happens during the S phase of the cell cycle? DNA replicates (copies) itself!

32. DNA Replication

33. DNA Replication • to make a copy of itself, DNA “unzips” C—G G-- --C T-- --A A-- --T G-- --C G-- --C

34. DNA Replication • new bases come in to make a new complementary strand C—G G--CG --C T--AT--A A--TA--T G--CG--C G--CG--C Notice these strands are the same.

35. Your turn • copy and complete the DNA strand C-- G-- G-- T-- A-- A-- C-- G--

36. Does it look like this? C--G G--C G--C T--A A--T A--T C--G G--C

37. “Unzip” and copy it! C—G G-- --C G-- --C T-- --A A-- --T A-- --T C-- --G G-- --C

38. Does it look like this? C—G G--C G--C G--C G--C T--A T--A A--T A--T A--T A--T C--G C--G G--C G--C

39. the main enzyme involved in DNA replication is DNA polymerase RESULTS in two identical DNA molecules! DNA Replication

40. SOL Review • When designing a scientific investigation, which of the following should be identified first? • A) lab equipment needed • B) appropriate sample size • C) useful analysis software • D) a testable hypothesis

41. 12-3: RNA and Protein Synthesis

42. RNA sugar: ribose DNA sugar: deoxyribose RNA vs DNA structure • single-stranded • double-stranded • uracil (U) base • thymine base

43. 3 Types of RNA RNA is mainly involved in PROTEIN SYNTHESIS • messenger RNA (mRNA) • ribosomal RNA (rRNA) • transfer RNA (tRNA)

44. Protein Synthesis • Transcription • RNA Editing • Translation Overview

45. Transcription • DNA is “transcribed” into an mRNA strand with the help of RNA polymerase

46. Transcription • how does RNA polymerase “know” where to start and stop making the RNA copy of DNA? • the promoter region of the DNA is the start (like the opening song) • then the middle part is the codingregion, or the gene (like the TV show) • the RNA polymerase stops at the terminationsequence, the end (like the credits)

47. RNA Editing • like a writer’s 1st draft • introns(intervening sequences) are removed • exons(expressed sequences) are left to make up the mRNA

48. Translation • mRNA “translated” into amino acids (which form proteins!) • occurs in the RIBOSOME

49. How does the ribosome “read” the mRNA? • using the GENETIC CODE! • this “code” only uses 4 letters: A, U, C, G • these 4 letters represent 20 different amino acids • the code is read 3 letters at a time (in triplicate) – these are called codons • example: RNA sequence UCGCACGGU would be read UCG CAC GGU

50. The Genetic Code • each codon represents an amino acid • there are 64 codonsthat code for 20 amino acids • 1 start: AUG • 3 stops: UAAUAG UGA