Chapter 9 and some of 8 DNA and the Molecular Structure of Chromosomes

1. Chapter 9 and some of 8DNA and the Molecular Structure of Chromosomes

2. Chapter Outline • Functions of the Genetic Material • Proof That Genetic Information Is Stored in DNA • The Structures of DNA and RNA • Chromosome Structure in Prokaryotes and Viruses

3. Functions of the Genetic Material The genetic material must replicate, control the growth and development of the organism, and allow the organism to adapt to changes in the environment.

4. Functions of the Genetic Material • Genotypic Function: Replication • Phenotypic Function: Gene Expression • Evolutionary: Allows for Mutation

5. Chromosomes • Genes are located on chromosomes. • Chromosomes contain proteins and nucleic acids. • The nucleic acids are deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).

6. Proof that Genetic Information is Stored in DNA In most organisms, the genetic information is encoded in DNA. In some viruses, RNA Is the genetic material. Viroids are infectious naked RNA molecules, and prions are infectious, heritable proteins (not TRUE).

7. DNA Mediates Transformation Convert IIR to IIIS By DNA?

8. Avery MacLeod and McCarty Experiment Circa 1943

9. The Genetic Material of Bacteriophage T2 is DNA

10. The Genetic Material of Tobacco Mosaic Virus is RNA

11. Viroids and Prions • Viroids are infectious, naked RNA molecules. • Prions are heritable (What do they mean here?), infectious proteins that do not contain nucleic acids.

12. Key Points • The genetic information of most living organisms is stored in deoxyribonucleic acid (DNA). • In some viruses, the genetic information is present in ribonucleic acid (RNA). • Viroids and prions are infectious naked molecules of RNA and protein, respectively.

13. The Structures ofDNA and RNA DNA is usually double-stranded, with adenine paired with thymine and guanine paired with cytosine. RNA is usually single-stranded and contains uracil in place of thymine.

14. nucleotide = sugar + base + phosphate nucleoside = sugar +base When Do we Find RNA Mixed with The DNA?

15. Ribonucleotide Reductase

16. Pyrimidines have the longer name and smaller base Purines have the shorter name and bigger base

18. Structure of aPolynucleotide Chain Why do we Always talk about DNA going in the 5’ to 3’ direction?

20. Deoxyribonucleotides What is dideoxyadenosine triphosphate (ddATP)? Why are dideoxynucleotides useful in Mol.Bio.?

21. One of Chargaff’s Rules

22. X-ray Diffraction Pattern of DNA

23. The Double Helix ? ? ? ?

26. I hate when DNA is not depicted properly!

27. DNA Structure • Complementary Base Pairs (A with T, G with C • Antiparallel Strands • Right-handed double helix (B-DNA) (No obvious reason to me why Right-handed is better than left-handed)

29. A-DNA, B-DNA and Z-DNA The Z-DNA helix is left-handed and has a structure that repeats every 2 base pairs. The major and minor grooves, unlike A- and B-DNA, show little difference in width

30. A-DNA, B-DNA and Z-DNA

31. Supercoiling(higher order structure)

32. What circular DNA exists in humans?

33. Key Points • DNA usually exists as a double helix, with the two strands held together by hydrogen bonds between the complementary base pairs: adenine paired with thymine and guanine paired with cytosine. • The complementarity of the two strands of a double helix makes DNA uniquely suited to store and transmit genetic information.

34. Key Points • The two strands of a DNA double helix have opposite chemical polarity. • RNA usually exists as a single-stranded HELIX containing uracil instead of thymine. Why Does RNA form a helical structure?

35. STACKING OF BASES

36. The DNA of Prokaryotes and Viruses • Prokaryotes are monoploid. • Most viruses and prokaryotes have a single set of genes stored in a single chromosome, which contains a single molecule of nucleic acid.

37. The E. coli Chromosome

38. Key Points • The DNA molecules in prokaryotic and viral chromosomes are organized into negatively supercoiled domains. • Bacterial chromosomes contain circular molecules of DNA segregated into about 50 domains.

39. The Genetics of Bacteria Bacteria contain genes that mutate to produce altered phenotypes. Gene transfer in bacteria is unidirectional—from donor cells to recipient cells.

40. Bacteria • One main chromosome with a few thousand genes. • Variable number of plasmids and episomes. • Asexual reproduction by simple fission.

41. Recombination in Bacteria Does this recombination process interfere with DNA cloning experiments?

42. Key Points • Bacteria usually contain one main chromosome. • Wild-type bacteria are prototrophs; they can synthesize everything they need to grow and reproduce given an energy source and some inorganic molecules. • Auxotrophic mutant bacteria require additional metabolites for growth.

43. Key Points • Gene transfer in bacteria is unidirectional; genes from a donor cell are transferred to a recipient cell, with no transfer from recipient to donor.

44. Mechanisms of Genetic Exchange in Bacteria Bacteria exchange genetic material through three different parasexual processes.

47. Transformation inBacillus subtilis (NOT TRUE for E.Coli)

48. Streptococcus pneumoniae Phenotypes

49. Transformation-Griffith’s Expt 1928