1. DNA History Structure Function

2. DNA Deoxyribonucleic Acid
Functions to control the production of proteins within the cell thus controlling all chemical processes within the cell

3. Discovery of DNA Function Fred Griffith
Transformation Experiments
Transfer of hereditary material from dead
S cells (virulent) to living R cells (nonvirulent) of a pneumonia-causing bacterium
Concluded something from the S cells (proteins or nucleic acids) had transformed the R cells

4. Mice injected with live cells of harmless strain R.
Mice injected with live cells of killer strain S.
Mice injected with live R cells plus heat-killed S cells.
Mice injected with heat-killed S cells.
Mice do not die. No live R cells in their blood.
Mice die. Live S cells in their blood.
Mice do not die. No live S cells in their blood.
Mice die. Live S cells in their blood.
Fig. 13.3, p. 216

5. Discovery of DNA Oswald Avery
Showed that Griffith’s “substance” was DNA
DNAase blocked the transformation

6. Discovery of DNA Function Hershey-Chase
Bacteriophage injects DNA--not protein--into bacterium
Radioisotope labeled protein and DNA of bacteriophage
Radioactive phosphorus is detected inside of bacteria

7. Bacteriophage genetic material bacterial cell wall plasma membrane
viral coat
sheath
base plate
tail fiber
cytoplasm
Fig. 13.4, p

8. Hershey-Chase virus particle labeled with 35S
virus particle labeled with 32P
Hershey-Chase
bacterial cell (cutaway view)
label outside cell
label inside cell
Fig. 13.5, p. 217

9. Nature of the Genetic Material
Property 1 - it must contain, in a stable form, information encoding the organism’s structure, function, development and reproduction
Property 2 - it must replicate accurately so progeny cells have the same genetic makeup
Property 3 - it must be capable of some variation (mutation) to permit evolution

10. Discovery of DNA Rosalind Franklin
used x-ray defraction to predict structure

11. X-ray diffraction photograph of the DNA double helix

12. Discovery of DNA James Watson and Francis Crick 1953
described the helical structure of DNA
Double helix
2 strands of hydrogen bonded nucleotides twisted around a central axis

13. 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 X Y

14. Structure of a nucleotide
A nucleotide is made of 3 components:
A Pentose sugar
This is a 5 carbon sugar
The sugar in DNA is deoxyribose.
The sugar in RNA is ribose.

15. Structure of a nucleotide
A Phosphate group
Phosphate groups are important because they link the sugar on one nucleotide onto the phosphate of the next nucleotide to make a polynucleotide.

16. Structure of a nucleotide
A Nitrogenous base
In DNA the four bases are:
Thymine
Adenine
Cytosine
Guanine
In RNA the four bases are:
Uracil

17. Nitrogenous bases Two types
Pyramidines
Thymine - T
Cytosine - C
Uracil - U
Purines
Adenine - A
Guanine - G

19. Sugar phosphate bonds (backbone of DNA)
Nucleotides are connected to each other via the phosphate on one nucleotide and the sugar on the next nucleotide
A Polynucleotide

21. Patterns of Base Pairing
DNA consists of two strands of nucleotides held together at bases by hydrogen bonds
Purines bond to Pyrimidines
This is because there is exactly enough room for one purine and one pyrimidine base between the two polynucleotide strands of DNA.
Amount of A=T and C=G

22. Double Helix of DNA

23. DNA Replication and Repair
DNA helicase causes the two strands of the double helix to unwind at one "origin" (viral/bacterial) or many origins (eukaryotic);
Unwinding and assembly proceeding simultaneously in both directions at replication forks exposing the bases of the two strands of DNA

24. DNA Replication and Repair
 Unattached nucleotides pair with exposed bases
DNA polymerases assemble the nucleotides into nucleic acids and "proofread" the new bases for mismatched pairs, which are replaced with correct bases
DNA ligase seals the bases up
 Gyrase winds the DNA molecules
Replication resulting in 2 molecules that consist of one "old" strand and one "new" strand

25. Origins initiate replication at different times.

27. Fig. 13.9, p. 220

28. continuous
assembly on
one strand
discontinuous
assembly on
other strand
newly
forming
DNA
strand
one
parent
DNA
strand
Fig , p. 221

29. Replication of DNA and Chromosomes
Speed of DNA replication: 3,000 nucleotides/min in human ,000 nucleotides/min in E.coli
Accuracy of DNA replication: Very precise (1 error/1,000,000,000 nt)

30. Questions?
Of the 4 bases, which other base does adenine most closely resemble?
List the 4 different nucleotides.
Which 2 molecules of a nucleotide form the sides of a DNA ladder?

32. Questions?
If 30% of a DNA molecule is Adenine, what percent is Cytosine?
What does the term replication mean?
What is another name for adenine, ribose and three phosphate molecules attached to it?

33. From DNA to Proteins

34. The Three Classes of RNA
Messenger RNA (mRNA)
 carries the "blueprint" for protein assembly to the ribosomes
Ribosome RNA (rRNA)
combines with proteins to form ribosomes upon which polypeptides are assembled
Transfer RNA (tRNA)
brings the correct amino acid to the ribosome and pairs up with an mRNA code for that amino acid

35. Structure of an RNA Nucleotide
RNA composed of nucleotides
Ribose
Phosphate group
Bases
Adenine
Cytosine
Guanine
Uracil

36. GUANINE ADENINE (G) (A) base with a base with a double-ring
structure
ADENINE
(A)
base with a
double-ring
structure
CYTOSINE
(C)
base with a
single-ring
structure
URACIL
(U)
base with a
single-ring
structure
Fig. 13.6, p. 218

37. How RNA is Assembled
Base pairing
A - U
C - G

38. Transcription Nucleotide assembled Portion of DNA serves as template
(5’ ---> 3’ direction)
RNA polymerase
3 types in eukaryotes to make the 3 types of RNA
Promoter signals start of a gene

39. Transcription Helicase unwinds the DNA molecule
RNA polymerase matches down a RNA base with the appropriate DNA base
Ligase seals the RNA strand
RNA now leaves the DNA molecule and the nucleus
Gyrase winds up the DNA strand

40. Finishing Touches on the mRNA Transcripts
Modification
Introns
Snipped out
Exons
Are translated

41. unit of transcription in a DNA strand
exon
intron
exon
intron
exon 3’ 5’
transcription into pre-mRNA
poly-A
tail
cap 5’ 3’
(snipped out)
(snipped out) 5’ 3’
mature mRNA transcript
Fig. 14.9, p. 229

42. An Overview DNA unwinds mRNA copy is made of one of the DNA strands.
mRNA copy moves out of nucleus into cytoplasm.
tRNA molecules are activated as their complementary amino acids are attached to them.

43. An Overview
mRNA copy attaches to the small subunit of the ribosomes in cytoplasm. 6 of the bases in the mRNA are exposed in the ribosome.
A tRNA bonds complementarily with the mRNA via its anticodon.
A second tRNA bonds with the next three bases of the mRNA, the amino acid joins onto the amino acid of the first tRNA via a peptide bond.

44. An Overview
The ribosome moves along. The first tRNA leaves the ribosome.
A third tRNA brings a third amino acid
Eventually a stop codon is reached on the mRNA. The newly synthesised polypeptide leaves the ribosome.

45. The Genetic Code Codons On mRNA Triplets
RNA polymerases read nucleotide bases
Cells have 64 kinds of codons
Only 20 amino acids

46. Fig , p. 230

47. Protein Synthesis: An Example
DNA Sequence: TAC GGA GGT TGA ACT
mRNA: AUG CCU CCA ACU UGA
tRNA: UAC GGA GGU UGA ACU
Amino Acids: met – pro - pro – thr - stop

48. Role of tRNA
tRNA
Attachment site for amino acid
Anticodon

49. Role of rRNA
rRNAs are components of ribosomes

50. Summary

51. Translation Initiation Elongation Termination
tRNA and mRNA are loaded onto a ribosome
Elongation
Polypeptide chain forms as mRNA passes between ribosome subunits
Termination
Stop codon and detachment of mRNA and polypeptide chain

52. Translation
In cytoplasm
3 stages
Initiation
Elongation
Termination

53. mRNA attaches to small ribosomal subunit

56. End of Translation

57. Translation - Animation

60. One Gene, One Polypeptide
Sickle Cell Anemia
Hemoglobin S and A
Gene mutation
Affects protein synthesis
Amino acid sequences of polypeptide chains are encoded in genes

61. Fig. 14.5, p. 227 VALINE PROLINE THREONINE LEUCINE HISTIDINE GLUTAMATE