1. DNA & RNA
Introduction to HE.5.B.2 Describe the Watson-Crick double helix model of DNA, using the base paring rule (adenine-thymine, cytosine-guanine)

2. Frederick Griffith

3. Frederick Griffith Birth date: 1879 Birth place:: England, UK
Nationality: British
Death date: 1941, London, UK
Education: University of Liverpool
Griffith experiment, 1928 that demonstrated bacterial transformation
His discovery showed the central role of DNA in heredity.
Discovered the existence of a “transforming factor”.

4. Griffith Experiment

5. Griffith Experiment – What is the big deal?
TRANSFORMATION: one strand of bacteria had been changed permanently into another.
The factor transferred must contain information and since it can be inherited the transforming factor might be a gene.
This means:
Genetic information could be transferred from one bacterium to another.

6. Oswald Avery

7. Oswald Avery Birth date: October 21, 1877
Birth place: Halifax, Nova Scotia
Nationality: Canadian (and American citizenship)
Death date: February 20, Nashville, Tennessee
Education: Colgate University & Columbia College of Physics and Surgeons.
Physician and medical researcher, was nominated for a Nobel multiple times but was never awarded.
Questioned the controls used in Griffith experiment
Identified DNA as the transforming factor.

8. Avery’s Experiment
Used enzymes to break down proteins, lipids, carbohydrates and other molecules including RNA to find out if transformation would still occur.
Transformation did not happen when enzymes destroyed DNA.
Avery discovered that the nucleic acid DNA stores and transmits genetic information from one generation of an organism to the next.

9. Alfred Hershey

10. Alfred Hershey Birth date: December 4, 1908. Birth place: Owosso, MI
Nationality: American
Death date: May 22, New York
Education: Michigan State University
Bacteriologist and geneticist
Received a Nobel prize for the discovery of virus replication
His work with Martha Chase provided more evidence that DNA, not protein, was the genetic material of life

11. Martha Chase

12. Martha Chase Birth date: November 30, 1927
Birth place: Cleveland Heights, OH
Nationality: American
Death date: August 8, Ohio
Education: The College of Wooster and PhD from Universidad de Puerto Rico
Geneticist
Her career was cut short because due to dementia
Her work with Alfred Hershey provided more evidence that DNA, not protein, was the genetic material of life

13. Hershey-Chase Experiment
The Hershey-Chase Experiment Alfred Hershey and Martha Chase used different radioactive markers to label the DNA and proteins of bacteriophages. The bacteriophages injected only DNA into the bacteria, not proteins. From these results, Hershey and Chase concluded that the genetic material of the bacteriophage was DNA.

15. Why was their experiment important?
Their experiment concluded the genetic material was DNA not protein.

16. Erwin Chargaff

17. Erwin Chargaff Birth date: August 11, 1905
Birth place: Czernowitz, Austria-Hungary
Nationality: Austrian (and American citizenship)
Death date: June 20, New York, NY.
Education: University of Vienna & Yale University
Biochemist, received the Pasteur Medal and National Medal of Science
Discovered the Chargaff’s rule that helped determine the structure of DNA.

18. Rosalind Franklin

19. Rosalind Franklin Birth date: July25, 1920
Birth place: Notting Hill, United Kingdom
Nationality: British
Death date: April 16, London, United Kingdom
Education: University of Cambridge.
Biophysicist and x-ray crystallographer. Her images were used by Watson and Crick without her permission
Her x-ray crystallography images of DNA helped determine the molecular structure of DNA.

20. DNA X-ray Crystallography

21. Francis Crick

22. Francis Crick Birth date: June 8, 1916
Birth place: Northempton, United Kingdom
Nationality: British
Death date: July 28, San Diego, CA.
Education: University College, London.
Molecular biologist, biophysicist and neuroscientist. Received a Nobel prize in 1962.
Co-discovered the structure of the DNA molecule with James Watson.

23. James Watson

24. James Watson Birth date: April 6, 1928 Birth place: Chicago, IL
Nationality: American
Death date: -
Education: Indiana University, Bloomington
Molecular biologist, geneticist and zoologist. Received a Nobel Prize in 1962.
Co-discovered the structure of the DNA molecule with Francis Crick.

27. The component and Structure of DNA
What we know at this point:
Genes were made of DNA
Genes are a set of instructions that determine what the organism is like, its appearance, how it survives, and how it behaves in its environment
What are we going to find out:
How DNA carry information, how they put the information to work, and how it can be easily copied.

28. 3 Critical things genes can do:
Carry information from one generation to the next.
Have to put that information to work by determining the heritable characteristics of organisms.
Easily copied, because all of a cell’s genetic information is replicated every time a cell divides.

29. What is DNA made of?
NUCLEOTIDES Nucleotides have three parts: Phosphate, Deoxyribose sugar (5 carbon sugar) and Nitrogenous base.

30. So What is DNA?
DNA is a long molecule made of units called nucleotides.

31. The 4 Nitrogenous Bases:
There are four kinds of nitrogenous bases in DNA

32. Chargaff’s Rules Organism %A %G %C %T A/T G/C %GC %AT Maize 26.8 22.8
23.2
27.2
0.99
0.98
46.1
54.0
Octopus
33.2
17.6
31.6
1.05
1.00
35.2
64.8
Chicken
28.0
22.0
21.6
28.4
1.02
43.7
56.4
Rat
28.6
21.4
20.5
1.01
42.9
57.0
Human
29.3
20.7
20.0
30.0
1.04
40.7
59.3
Grasshopper
41.2
58.6
Sea Urchin
32.8
17.7
17.3
32.1
35.0
64.9
Wheat
27.3
22.7
27.1
45.5
54.4
Yeast
31.3
18.7
17.1
32.9
0.95
1.09
35.8
64.4
E. coli
24.7
26.0
25.7
23.6
51.7
48.3

33. Chargaff’s Rule
The percentage of guanine (%G) and cytosine (%C) bases are almost equal in any sample of DNA. The same is true for adenine (%A) and thymine (%T).
[A] = [T] and [G] = [C]
Why is this important? It gave scientists clues on the structure of DNA.

34. X-Ray Evidence
X-ray diffraction gave even more clues on the structure of DNA.

35. So what happens when you add the clues together?
X-RAY CRYSTALLOGRAPHY
NUCLEOTIDES
Organism %A %G %C %T
A/T
G/C
%GC
%AT
Maize
26.8
22.8
23.2
27.2
0.99
0.98
46.1
54.0
Octopus
33.2
17.6
31.6
1.05
1.00
35.2
64.8
Chicken
28.0
22.0
21.6
28.4
1.02
43.7
56.4
Rat
28.6
21.4
20.5
1.01
42.9
57.0
Human
29.3
20.7
20.0
30.0
1.04
40.7
59.3
CHARGAFF’S RULE

36. THE DOUBLE HELIX

37. DNA Summary

38. DNA Extraction Lab

39. Let’s build our own DNA model

40. DNA Replication

41. The Structure of RNA
RNA, like DNA, is made of a long chain of nucleotides.
Each nucleotide is made up of a 5-carbon sugar, a phosphate group, and a nitrogenous base.

42. Figure A represents an RNA nucleotide while figure B represents a DNA nucleotide. Compare both figures
How are DNA and RNA nucleotides similar?
How are DNA and RNA nucleotides different?

43. There are three main differences between RNA and DNA:
1) DNA has the sugar ___________________ and RNA has the ___________________ sugar.
2)?
3)?

44. Compare the RNA nucleotide strand to the DNA nucleotide strand.
What are the nitrogenous bases found in RNA?
What are the nitrogenous bases found in DNA?
How does the RNA strand compares do the DNA strand?

45. There are three main differences between RNA and DNA:
1) DNA has the sugar ___________________ and RNA has the ___________________ sugar.
2) DNA is ___________ stranded and RNA is ________ stranded.
3)DNA has the base ____________ and RNA has the base ____________.

46. RNA VS DNA

47. What are the roles of RNA and DNA?
Both molecules are needed in protein synthesis (making proteins).
DNA stores and transmits genetic information.
The main job of RNA is to transfer the genetic code needed for the creation of proteins from the nucleus to the ribosome.
This process prevents the DNA from having to leave the nucleus, so it stays safe.

48. Types of RNA
RNA molecules are involved in just one job – protein synthesis.
RNA controls the assembly (putting together) of amino acids into proteins.
There are 3 types of RNA molecules that work together to get the job done.
Messenger RNA
Transfer RNA
Ribosomal RNA

49. Messenger RNA (mRNA)

50. Transfer RNA (tRNA)

51. Ribosomal RNA (rRNA)

52. What is a gene?

53. TRANSCRIPTION AND TRANSLATION
How are proteins made?
Proteins happen in 2 steps:
TRANSCRIPTION AND TRANSLATION

54. TransCription
TRANSCRIPTION: RNA molecules are made by copying part of the nucleotide sequence of DNA into a complementary sequence in RNA.
This step happens in the nucleus and uses an enzyme, called RNA polymerase.
During transcription, RNA polymerase binds to DNA and separates the DNA strands. RNA polymerase then uses one strand of DNA as a template (model) from which nucleotides are put together into a strand of RNA.
Notice that in RNA the base Thymine is replaced by Uracil.
Promoters are sequences in the DNA that tells the RNA polymerase where to bind (attach) to make RNA

55. TRANSCRIPTION

56. TransLation
The decoding of an mRNA into a polypeptide (chain of amino acids), and it takes place in the ribosomes.
During translation, the cells use information from messenger RNA to produce proteins.
Translation begins when an mRNA molecule moves from the nucleus of the cell into the cytoplasm and attaches to a ribosome.
The genetic code carried by the mRNA is read three letters (nucleotides) at a time.
A codon consists of three nucleotides that specify a single amino acid that is to be added to the polypeptide chain.
As each codon of the mRNA molecule moves through the ribosome, the proper amino acid is brought into the ribosome by tRNA. In the ribosome, the amino acid is transferred to the growing polypeptide chain.
The anticodon is the name of the three unpaired bases on tRNA. The anticodon is complementary to one mRNA codon.

57. TRANSLATION

58. RNA molecules at work

59. How proteins are made:
Proteins are made by joining amino acids into long chains called polypeptides. Each polypeptide contains a combination of any or all of the 20 different amino acids found in nature.
The properties of proteins are determined by the order in which different amino acids are joined together to produce polypeptides.

60. How can the code with just four letters carry instructions for 20 different amino acids?
This is possible because the genetic code is read three letters at a time. Because there are four different bases, there are 64 possible codons of the genetic code. As you can see on the image below, some amino acids can be specified by more than one codon.

61. Amino Acid Table

62. Protein Synthesis