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. Martha Chase & Alfred Hershey
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. Chargaff’s Rule Adenine must pair with Thymine
Guanine must pair with Cytosine
Their amounts in a given DNA molecule will be about the same. T A G C

8. X-ray Photograph of DNA
The periodicity of the arcs on this photograph 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. Four features summarize the molecular architecture of DNA:
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 nitrogenous bases point toward the center of the helix.
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
III.The helix is generally right handed. However left handed Z-DNA exists.

19. Different forms of DNA Parameters A Form B Form Z-Form
Direction of helical
rotation
Right
Left
Residues per turn of
helix 11 10
12 base pairs
Rotation of helix per
residue
(in degrees) 33 36
-30
Base tilt relative to
helix axis 20 6 7

20. Different forms of DNA Parameters A Form B Form Z-Form Major groove
narrow and deep
wide and deep
Flat
Minor groove
wide and shallow
Orientation of N-glycosidic Bond
Anti
Anti for Py, Syn for Pu
Comments
most prevalent within cells
occurs in stretches of alternating purine-pyrimidine base pairs

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

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

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

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

28. C G
H-bonds T A

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.