A nucleic acid is a macromolecule composed of nucleotide chains . These molecules carry genetic information or fo

1. A nucleic acid is a macromolecule composed of nucleotide chains. • These molecules carry genetic information or form structures within cells. • The most common nucleic acids are • deoxyribonucleic acid (DNA) and ribonucleic acid (RNA).. • Artificial nucleic acids include • peptide nucleic acid (PNA), • Morpholino • locked nucleic acid (LNA), • 4. Glycol nucleic acid (GNA) and threose nucleic acid (TNA).

2. DNA as Genetic Material • established by several critical experiments • Fred Griffith (1928) • Oswald T. Avery, C. M. MacLeod, and M. J. McCarty (1944) • Alfred D. Hershey and Martha Chase (1952)

3. 1944 - Avery, MacLeod & McCarty Purified DNA as transforming factor • Work not well-received • Protein more complex & better able to store information Oswald Avery Colin MacLeod Maclyn McCarty

4. 1952 - Hershey & Chase Viral DNA (not protein) programs cells Bacteriophages Martha Chase & Alfred Hershey

5. DNA • Discovery of the DNA double helix A. 1950’s Chargaff’s Rule B. Rosalind Franklin- X-ray photo of DNA. C. Watson and Crick- described the DNA molecule from Franklin’s X-ray.

6. Chargaff’s Rules: [A] = [T] [G] = [C] [A] + [G] = [T] + [C] purines pyrimidines

7. C T A G Chargaff’s Rule • Adeninemust pair with Thymine • Guanine must pair with Cytosine • Their amounts in a given DNA molecule will be about the same.

8. X-ray Photograph of DNA • The periodicity of the arcs on thisphotograph indicated that: • DNA had a regular helical structure. • There are regular repeats every 3.4 and 34 Angstroms

9. DNA structure and Replication Chapter 16

10. The Structure of DNA • Four features summarize the molecular architecture of DNA: • The DNA molecule is a double-stranded helix. • The diameter of the DNA molecule is uniform. • The twist in DNA is right-handed. • The two strands run in different directions (they are antiparallel).

11. The Structure of DNA • The sugar–phosphate backbones of each strand coil around the outside of the helix. • The nitrogenous bases point toward the center of the helix. • Hydrogen bonds between complementary bases hold the two strands together. • A always pairs with T (two hydrogen bonds). • G always pairs with C (three hydrogen bonds).

12. WATSON AND CRICK MODEL 1. A double helix with regular dimensions. Two antiparallel chains. 2. The sugar phosphate backbone is out; the bases are inside the helix. 3. The helix is right handed. 4. MAJOR POINT: The two chains are held together by hydrogen bonds.

13. The Double Helix

14. Space Filling Model

15. The sugar phosphate backbone is outside; • the bases are inside.

16. Major forces holding the helix together: 1.base stacking forces 2.hydrophobic interactions among the bases 3.hydrogen bonds

17. III.The helix is generally right handed. However left handed Z-DNA exists.

19. Different forms of DNA

20. Different forms of DNA

21. Deoxyribonucleic Acid (DNA) • Made up of nucleotides (DNA molecule) in a DNA double helix. • Nucleotide: 1. Phosphate group 2. 5-carbon sugar 3. Nitrogenous base • ~2 nm wide

23. Phosphate Group O O=P-O O 5 CH2 O N Nitrogenous base (A, G, C, or T) C1 C4 Sugar (deoxyribose) C3 C2 DNA Nucleotide

24. 5 O 3 3 O P P 5 5 C O G 1 3 2 4 4 2 1 3 5 O P P T A 3 5 O O 5 P P 3 DNA Double Helix

25. A or G T or C Nitrogenous Bases • PURINES 1. Adenine (A) 2. Guanine (G) • PYRIMIDINES 3. Thymine (T) 4. Cytosine (C)

27. BASE-PAIRINGS Base # of Purines Pyrimidines PairsH-Bonds Adenine (A)Thymine (T) A = T 2 Guanine (G)Cytosine (C) C G 3

28. H-bonds G C A T

31. Question: • If there is 30%Adenine, how much Cytosine is present?

32. There would be 20%Cytosine. Adenine (30%) = Thymine (30%) Guanine (20%) = Cytosine (20%) (50%) = (50%)

33. Figure 11.7 Base Pairing in DNA Is Complementary

34. The genetic material performs four important functions: • It stores all of an organism’s genetic information. • It must be precisely replicated in the cell division cycle. • It is expressed as the phenotype. • It is susceptible to mutation.

35. Watson & Crick predicted that each DNA strand could serve as a template for the replication of a new strand Q: What is the mode of replication?

36. RNA

37. 4 types of RNA • tRNA (transfer RNA) • mRNA • rRNA • snRNA

38. tRNA There are 4 arms and 3 loops. The acceptor, D,T pseudouridine C and anticodon arms, D, T pseudouridine C and anticodon loops. Sometimes tRNA molecules have an extra or variable loop (this is shown in yellow in the adjacent figure).

39. mRNA

40. r RNA

41. ribosomal RNA is found in the ribosomes. Prokaryotic ribosomes have 3 rRNA molecules: 23S, 16S and 5S. Eukaryotic ribosomes have 4 rRNA molecules: 28S, 18S, 5.8S and 5S.

42. snRNA • Small nuclear RNA (snRNA)-number of small RNA molecules found in the nucleus. • These RNA molecules are important RNA splicing (removal of the introns from hnRNA) and maintenance of the telomeres, or chromosome ends. • They are always found associated with specific proteins and the complexes are referred to as small nuclear ribonucleoproteins (SNRNP) or sometimes as snurps. • Antibodies against snurps are found in a number of autoimmune diseases.