1. Franklin’s photo below proved model on left to be correct for DNA
Crick
Watson
Franklin
Wilkins
Franklin’s photo below proved model on left to be correct for DNA
Pauling

2. Most important scientific paper in Biology in last 100 years
First time DNA double helix seen in print
Most important scientific paper in Biology in last 100 years
By Watson and Crick, 1953

3. 2 April 1953 MOLECULAR STRUCTURE OF NUCLEIC ACIDS
A Structure for Deoxyribose Nucleic Acid
“We wish to suggest a structure for the salt of deoxyribose nucleic acid (D.N.A.). This structure has novel features which are of considerable biological interest.”
From the original Watson and Crick article – first published “double helix” diagram

4. Proof of double helix

5. Summary of a few people involved with DNA:
Pauling and Corey – “telephone pole” model for DNA
Franklin – x-ray photos proved Pauling wrong
Wilkins – gave x-rays to Watson and Crick
Watson, Crick, Wilkins – Nobel Prizes for DNA structure
Watson & Crick
Pauling and Corey

6. First to describe the physics to split the atom
Rosalind Franklin 06
Lise Meitner
Nobel Prize
Otto Hahn
Nobel Prizes
Figure: 13-02a
Title: DNA Investigator
Caption: (a) DNA Investigator
Rosalind Franklin, whose work in X-ray diffraction was important in revealing the structure of the DNA molecule.
First to discover structure of DNA
First to describe the physics to split the atom

7. Basic Terms: DNA Nucleotide (monomer) Subcomponents of nucleotide
sugar = deoxyribose
phosphate
bases – 4 of them
adenine (A) guanine (G) cytosine (C) thymine (T)
Nucleic Acid (polymer) – chain of nucleotides
Double helix – two chains of nucleic acids

8. DNA Nucleotide B B B B B S P S S S P S P P P B S P
Nucleic acid (polymer) = chain of nucleotides (monomers) B B B B B S P S S S P S P P P B
Base = A, G, C, T
phosphate
Nucleotide (DNA or RNA) S P
sugar
DNA Nucleotide

9. Double helix of nucleic acid
Sugar phosphate base
Double helix of nucleic acid
Figure: 13-03b
Title: Component Molecules of DNA
Caption: The Structure of DNA
Nucleotide

10. Base Pairing in DNA double helix
G-C
A-T
C-G
T-A

11. Only one base pairing is possible

12. Nucleosome = protein + DNA

13. Nucleosomes

14. Euchromatin = active DNA = decondensed
Heterochromatin = inactive DNA = condensed
Nucleosome
DNA
Euchromatin = active DNA = decondensed
Fig

15. DNA Replication

16. One double helix forms two identical double helices
DNA replication:
One double helix forms two identical double helices
Figure: 13-04
Title: DNA Replication
Caption: The result of DNA replication is two identical molecules of DNA, whereas the process began with one.

17. Double Helix separates New strands forms by base pairing
Figure: 13-05
Title: How Life Builds on Itself
Caption: Each newly synthesized DNA molecule is a combination of the old and the new. An existing DNA molecule unwinds, and each of the resulting single strands (the old) serves as a template for a complementary strand that will be formed through base pairing (the new).

18. Double helix separatesC A T G C A G
Double helix separates T A T

19. Base pairing
New nucleotides are added to the “old” or original DNA nucleotides by base pairing with the help of enzymes (not shown here)

20. normal
Mutant
Fig

21. Protein Synthesis

22. Review
Protein gives life structure
Protein gives life function
Amino acid sequence gives protein its structure and function
Question: How is amino acid sequence determined?

23. Gene = section of DNA that codes for amino acid sequence in a protein
Yeast Fruit Fly Worm Green Plant
6034 genes ,061 genes ,099 genes ,000 genes
Gene = section of DNA that codes for amino acid sequence in a protein
Figure: 14-13
Title: Not as Much Difference as We Thought
Caption: At one time, scientists assumed that the human genome contained about 100,000 genes. Genome sequencing revealed, however, that the human genome probably contains about 30,000 genes. This is only about 11,000 more genes than the tiny roundworm C. elegans, and about 17,000 more than the Drosophila fruit fly. Scientists can make comparisons among genomes because, though the human genome has gotten most of the attention, the genomes of several other organisms have now been sequenced as well, including those shown here.

24. DNA (m)RNA (copy) Protein
Transcription
Translation

25. Retire already!!! Overview Figure: 14-02
Title: The Two Major Stages of Protein Synthesis
Caption: The Two Major Stages of Protein Synthesis

26. Sugar–phosphate backbone Base pairing is the genetic code
G-C
C-G
A-T
T-A

27. DNA double helix separates RNA nucleotides attach to DNA
T replaced by U
Figure: 14-04a
Title: Transcriptions Works through Base Pairing
Caption: Thanks to their chemical similarity, DNA and RNA can engage in base pairing, and this base pairing is how RNA transcripts are synthesized. The enzyme complex RNA polymerase undertakes two tasks in transcription: It unwinds the DNA sequence to be transcribed, and it brings together RNA nucleotides with their complementary DNA nucleotides, thus producing an RNA chain.
Base pairing makes RNA copy of DNA

28. Transcription = (m)RNA copy of one side of DNA

29. Transcription of mRNA DNA mRNA transcript DNA Figure: 14-04b
Title: Transcriptions Works through Base Pairing
Caption: Thanks to their chemical similarity, DNA and RNA can engage in base pairing, and this base pairing is how RNA transcripts are synthesized. The enzyme complex RNA polymerase undertakes two tasks in transcription: It unwinds the DNA sequence to be transcribed, and it brings together RNA nucleotides with their complementary DNA nucleotides, thus producing an RNA chain.

30. Codon = three RNA nucleotides = code for particular amino acid

31. Translation – conversion of mRNA nucleotide sequence (codons) into amino acid sequence of protein
Figure: 14-06
Title: Triplet Code
Caption: Each triplet of DNA bases codes for a triplet of mRNA bases (a codon), but it takes a complete codon to code for a single amino acid.

32. Codon – group of three mRNA nucleotides
Each amino acid has at least one specific codon.
Alanine (Ala) has the codon GCU.
Glycine has the codon GGU
Tyrosine has the codon UAU
Figure: 14-T01
Title: Amino Acids
Caption: Amino Acids

33. review
Codon = three RNA nucleotides = code for particular amino acid

34. Translation = mRNA codons place amino acids in proper order
review
Nontranscribed strand 5’
Transcription
DNA 3’
Transcribed strand
Codon 1
Codon 2
Codon 3
Codon 4
Codon 5
Codon 6
Polypeptide
Translation

35. UV-A
UV-B
Sun screen products
Human skin

36. Thymine Dimer mutation DNA from U.V. light
A C G T T C C A
T G C A A G G T
Thymine Dimer mutation DNA from U.V. light
UV light
A C G T T C C A
T G C A A G G T

37. Thymine dimer removed DNA repair enzymes
New DNA replaces hole left by damaged DNA

39. Every cell in the body has the same DNA, but each specific type of cell makes proteins unique to those cells?
In other words every cell in your body has the exact same book of blueprints but only certain pages are read in certain cells.

40. Human embryos are totipotent = can become any cell in the human body
Why?
because it has DNA to make every cell in the body.

41. 4 week old embryo is pluripotent – produce most cells
6 day old embryo is totipotent – produce all cells

42. Salamander – many tissues can be regenerated if damaged.

43. Salamander can re-grow new limbs because adult stem cells behave like embryonic cells.

44. Transcription of DNA to make new leg
Heterochromatin - inactive
Salamander leg cells damaged
Nucleosome
Euchromatin - active
DNA
Transcription of DNA to make new leg

45. Polymerase Chain Reaction

46. Small amount of DNA left at crime scene
Polymerase Chain Reaction (PCR)
DNA replication
After 20 replications (a few hours) – over 1,000,000 helices formed

47. DNA
DNA
Restriction enzyme (Eco R1) cuts DNA into fragments

48. DNA fragments loaded into wells in gel (like Jell-O)
Figure: 15-UNSB1
Title: Visualizing Lengths of DNA
Caption: In gel electrophoresis, negatively charged DNA fragments travel through the porous gel toward the positive end of the tray when a charge is applied to the gel. Large fragments, however, do not travel as far in a given amount of time as small fragments. Thus the fragments separate out by size. The first ÅgstripeÅh at the top of a lane represents a collection of fragments of a given size, the second stripe a second collection of fragments of a smaller size, and so on.
Fragments (-) migrate through gel because of electric current

49. DNA fragments have (-) charge
(+)

50. DNA fingerprinting – compares fragments of DNA formed by restriction enzymes
Like a barcode

52. Baby’s DNA
Father #1
Father #2