1. DNA / Protein Synthesis

3. History of DNA Research
DNA – Deoxyribonucleic acid
1) Frederick Griffith (1928)- discovered that a factor in heat-killed, disease-causing bacteria can “transform” harmless bacteria into ones that can cause disease.

4. Griffith's Experiments
Griffith set up four individual experiments.
Experiment 1: Mice were injected with the disease-causing strain of bacteria. The mice developed pneumonia and died.
Griffith injected mice with four different samples of bacteria. When injected separately, neither heat-killed, disease-causing bacteria nor live, harmless bacteria killed the mice. The two types injected together, however, caused fatal pneumonia. From this experiment, biologists inferred that genetic information could be transferred from one bacterium to another.

5. Experiment 2: Mice were injected with the harmless strain of bacteria
Experiment 2: Mice were injected with the harmless strain of bacteria. These mice didn’t get sick.
Harmless bacteria (rough colonies)
Griffith injected mice with four different samples of bacteria. When injected separately, neither heat-killed, disease-causing bacteria nor live, harmless bacteria killed the mice. The two types injected together, however, caused fatal pneumonia. From this experiment, biologists inferred that genetic information could be transferred from one bacterium to another.
Lives

6. Experiment 3: Griffith heated the disease-causing bacteria
Experiment 3: Griffith heated the disease-causing bacteria. He then injected the heat-killed bacteria into the mice. The mice survived.
Heat-killed disease-causing bacteria (smooth colonies)
Griffith injected mice with four different samples of bacteria. When injected separately, neither heat-killed, disease-causing bacteria nor live, harmless bacteria killed the mice. The two types injected together, however, caused fatal pneumonia. From this experiment, biologists inferred that genetic information could be transferred from one bacterium to another.
Lives

7. Heat-killed disease-causing bacteria (smooth colonies)
Experiment 4: Griffith mixed his heat-killed, disease-causing bacteria with live, harmless bacteria and injected the mixture into the mice. The mice developed pneumonia and died.
Harmless bacteria (rough colonies)
Griffith injected mice with four different samples of bacteria. When injected separately, neither heat-killed, disease-causing bacteria nor live, harmless bacteria killed the mice. The two types injected together, however, caused fatal pneumonia. From this experiment, biologists inferred that genetic information could be transferred from one bacterium to another.
Live disease-causing bacteria (smooth colonies)
Dies of pneumonia

8. Heat-killed disease-causing bacteria (smooth colonies)
Griffith concluded that the heat-killed bacteria passed their disease-causing ability to the harmless strain.
Harmless bacteria (rough colonies)
Griffith injected mice with four different samples of bacteria. When injected separately, neither heat-killed, disease-causing bacteria nor live, harmless bacteria killed the mice. The two types injected together, however, caused fatal pneumonia. From this experiment, biologists inferred that genetic information could be transferred from one bacterium to another.
Live disease-causing bacteria (smooth colonies)
Dies of pneumonia

9. Transformation 
Griffith called this process transformation because one strain of bacteria (the harmless strain) had changed permanently into another (the disease-causing strain).
Griffith hypothesized that a factor must contain information that could change harmless bacteria into disease-causing ones.

10. History of DNA Research
2) Oswald Avery (1944)- discovered DNA was responsible for transformation

11. History of DNA Research
3) Hershey and Chase (1952)- their studies supported Avery’s work by studying bacteriophage (a virus that infects bacteria)

13. History of DNA Research
4) Watson and Crick (1953)- first to develop a double-helix model of DNA

14. DNA
DNA is found inside the nucleus of every cell in your body

15. DNA Structure DNA is made up of nucleotides. Nitrogenous Base
Phosphate
Sugar

16. Parts of a nucleotide A nucleotide contains three parts:
1) Phosphate group
2) 5-carbon sugar group (deoxyribose)
3) Nitrogenous bases (4 types)
Adenine (A)
Guanine (G) Purines (double rings)
Cytosine (C)
Thymine (T) Pyrimidines (single ring)
To help you remember:
CUT = PY

18. Chargaff’s Rule
Erwin Chargaff (1949) discovered the base-pairing rules for nitrogenous bases:
1) A always pairs with T
C always pairs with G
2) % A in DNA = % T in DNA
% C in DNA = % G in DNA

19. Guanine
Cytosine
Adenine
Thymine

20. Double Helix
DNA molecule is composed of two long chains of nucleotides twisted and held together by hydrogen bonds in the center between the nitrogen bases

21. DNA Double Helix

22. In even in your smallest chromosome there are 30 million base pairs
In even in your smallest chromosome there are 30 million base pairs. How does so much DNA fit in every tiny cell in your body?

23. Much more fits when you organize and fold it.
DNA
You fold it!
Think about how much easier it is to pack your suitcase when everything is nicely folded.
Can’t fit
Much more fits when you organize and fold it.

24. DNA must condense (make itself smaller) by folding itself around proteins called Histones.
When DNA wraps around Histones it forms tight coils and is called chromatin.

25. What are histones? What is Chromatin?
Histones are proteins that DNA wraps around.
What is Chromatin?
Chromatin is what you call DNA when it is wrapped around the Histones.

26. Example:
Histone
DNA
Double Helix
Chromatin
DNA around histones

27. Chromosomes
When the chromatin forms coils and condenses it forms a chromosome.
See Fig in your book.

28. DNA
Double Helix
Chromosomes
Made up of chromatin
Chromatin
DNA around histones
Histone =

29. http://www.biostudio.com/demo_freeman_dna_coiling.htm (dna coiling)
DNA Double Helix  Chromatin  Chromosome
DNA Double Helix
DNA Chromatin
DNA Chromosome
(dna coiling)

30. DNA Replication
Occurs when cells divide.
(Cell division)

31. DNA Replication DNA makes an exact copy of itself
takes place inside the nucleus during S phase before cell division

32. Replication
Each strand of the double helix of DNA serves as a template against which the new strand is made.

33. A compliments T T compliments A G compliments C C compliments G
DNA Base Pairing Rules
Sugar-phosphate
Sugar-phosph
phosphate
A compliments T
T compliments A
G compliments C
C compliments G G A C T T C A A G T

34. Replication
Template strand
Step 1: The hydrogen bonds between the double helix break and two strands separate. Each strand is called a template strand.
Step 2: Two new complementary strands are formed following the rules of base pairing. The new strands are called complimentary strands.
Compliment strand

35. How DNA Replication Works!
DNA polymerase is an enzyme that adds the complimentary bases to the DNA template strand and also “proofreads” or checks that it is correct.
DNA Polymerase T A

36. Semiconservative

37. Template Strand (original) CGTATCCGGAATTT GCATAGGCCTTAAA
Replication
Template Strand (original)
CGTATCCGGAATTT
The complimentary strand..
GCATAGGCCTTAAA

38. Template strand
Complimentary Strand
ACGGCAT
TACGGCAT
TGCCGTA
ATGCCGTA

39. Complimentary
If I have a strand that DNA sequence of CAT what would be on the complimentary strand?
CAT
GTA

40. RNA Ribonucleic acid Single strand made up of nucleotides
contains three parts:
1) Phosphate group
2) 5-carbon sugar group (ribose)
3) Nitrogenous bases (4 types)
Adenine (A)
Guanine (G) Purines (double rings)
Cytosine (C)
Uracil (U) Pyrimidines (single ring)

41. Base-pairing in RNA
1) A always pairs with U
2) C always pairs with G

42. Types of RNA Type Function Messenger RNA (mRNA)
Carries copies of instructions to make proteins
Ribosomal RNA (rRNA)
Is a part of ribosomes
Transfer RNA (tRNA)
Transfers each amino acid to the ribosome to help make proteins

43. Compare DNA and RNA 1) Sugars are different: Deoxyribose Ribose
H OH OH OH
H OH OH OH

44. Compare DNA and RNA DNA RNA 2) A, G, C,T A, G, C, U
(A–T, C-G) (A-U, C-G)
3) Double stranded Single stranded
4) only 1 type 3 types

45. Protein Proteins are made of building blocks called amino acids.
Proteins are different from one another by the sequence, or order, of their amino acids.

46. Protein There are 20 different amino acids.
Thousands of proteins can be made from these amino acids because there are many different orders that they can be in.

47. Proteins are made in two steps:
Transcription
Translation

48. What is transcription?
The process where mRNA is made from a DNA template
Transcription happens in the nucleus

49. What is translation?
Translation is the decoding of an mRNA message into a protein.
Translation takes place on ribosomes in the cytoplasm

50. Transcription Translation

51. Transcription
Protein synthesis begins when a strand of (A) DNA unravels.
The code for producing a protein is carried in the sequence of the (B) bases in the DNA.
Each group of three bases forms a codon, which represents a particular amino acid.

53. Transcription
One of the unwound strands of DNA forms a complementary strand called (C) mRNA.
This process is called transcription.
It takes place in the nucleus of the cells.

54. Bases
DNA
mRNA

55. Post-transcriptional modification
DNA is composed of coding and noncoding sequences
Noncoding region = Introns
Coding region = Exons (code for proteins)
During transcription, introns are cleaved and removed, while exons combine to form useful mRNA

56. Post-transcriptional modification
E I E I E
initial DNA
 introns cleaved
pre-mRNA
 exons combine
final mRNA

57. Now look at the right side of the picture.
The mRNA has moved into the cytoplasm, where it attaches to a (D) ribosome.
A phase of protein synthesis called translation then begins.
Ribosome
mRNA

58. A (E) tRNA approaches the ribosome.
At one end of this molecule are three bases known as an (F) anticodon.
At the ribosome, each anticodon lines up with its complementary codon on the mRNA.
tRNA
Anticodon
Codon
Anticodon

59. This occurs according to base pairing.
At the other end of tRNA, an (G) amino acid is attached.
As the ribosome moves along the strand of mRNA, new tRNAs are attached.
This brings the amino acids close to each other.

60. The amino acids are joined by peptide bonds, and the resulting strand is a protein.

61. Codon Chart To determine which amino acid we choose we use this chart:
CODON AMINO ACID
AGU
AGC
GGU

62. What are mutations?
Mutations are changes in the DNA sequence that affects the genetic information

63. Types of mutations:
Gene mutations result from changes in a single gene
Chromosomal mutations involve changes in whole chromosomes

64. Gene mutations:
Point mutations – affect only one nucleotide because they occur at a single point
Include substitutions, additions, and deletions
Frameshift mutations – when a nucleotide is added or deleted and bases are all shifted over, leaving all new codons.
Include additions and deletions
Substitutions don’t usually cause a frameshift

65. Substitutions DNA mRNA Amino acids Original TAC GCA TGG AAT
AUG CGU ACC UUA
Met – Arg – Thr – Leu
Substitution
TAC GTA TGG AAT
AUG CAU ACC UUA
Met – His – Thr - Leu
One base change

66. Insertions DNA mRNA Amino acids Original TAC GCA TGG AAT
AUG CGU ACC UUA
Met – Arg – Thr – Leu
Insertion
TAT CGT ATG GAA T
AUA GCA UAC CUU A
Ile – Ala – Tyr - Leu
Many base changes

67. Deletions

68. Chromosomal mutations:
Include deletions, duplications, inversions, and translocations.

69. Deletions involve the loss of all or part of a chromosome.

70. Duplications produce extra copies of parts of a chromosome.

71. Inversions reverse the direction of parts of chromosomes.

72. Translocations occurs when part of one chromosome breaks off and attaches to another.

73. Significance of Mutations
Many mutations have little or no effect on gene expression.
Some mutations are the cause of genetic disorders.