1st hour
TRANSCRIPT
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CHAPTER 4:CHAPTER 4:Expression Of Biological Expression Of Biological
InformationInformation(6 Hours)(6 Hours)
CHAPTER 4:CHAPTER 4:Expression Of Biological Expression Of Biological
InformationInformation(6 Hours)(6 Hours)
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CHAPTER 4:EXPRESSION OF BIOLOGICAL INFORMATION
4.1 DNA and Genetic Information (2 hrs)
4.2 DNA Replication (2 hrs)
4.3 Protein Synthesis (1½ hrs)
4.4 Lactose Operon (30 mins)
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4.1 DNA & Genetic Information
4.1.1 DNA structure – Watson and Crick Model4.1.2 DNA– as the carrier of genetic information4.1.3 Gene concept; one gene one polypeptide
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4.1: DNA Structure- Watson & Crick Model
DNA is a double-stranded polymer.
Each DNA molecule has 2 bonding:-
1) Phosphodiester linkage - has strong covalent bond.
2) Hydrogen bonding- maintained the helix shape- linked the 2 nitrogenous bases
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Nucleic Acid DNA RNA
Each nucleotide consists of:1 phosphate group
1 pentose sugar 1 organic/nitrogenous base
2 types of pentose sugar: Ribose : RNA Deoxyribose : DNA
DNA Structure
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There are 4 types of organic bases for DNA:-Purines ( double ringed structure ) Adenine (A) Guanine (G)
2. Pyrimidine ( two single ringed structure ) Cytosine (C) Thymine (T)
Adenine = ThymineGuanine = Cytosine
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DNA structure – Watson & Crick Model (Nobel Laureate)
Consist of 2 polynucleotide chains.Anti-parallel (opposite direction).Both chain are linked to the other by pairs of organic bases which are themselves joined by hydrogen bonds.
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O
CH2
Base
O P OH
O
OH
OH
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23’
4
5’
• Phosphate group
• Pentose Sugar (5C)
• Organic Bases
Nucleotide Basic Structure
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DNA
DNA molecule structure
5`
oP
oP
oP
oP
P
o
P
o
P
o
P
o
C
T
G
A
A
T
G
C
5` 3`
3` Hydrogen bond
phosphodiester linkageHydrogen bond
10BASIC STRUCTURE OF DNA
11BASIC STRUCTURE OF DNA
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IF…….
So…
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DNA as the carrier of genetic information Characteristic that are required of genetic material, can be
able to: store information
replicate, in order to be in each cell of growing organism
control expression of traits
Encode the sequence of proteins
Change in a controlled away, in order to ensure survival of a species in a changing environment
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• There are experiments that were conducted to prove that DNA is the genetic material.
Griffith Experiment (1931)Hereditary Information Can Pass between
Organisms
Avery, MacLeod & McCarty Experiment (Avery et. al.(1944))
Find out that the transforming agent is the DNA
Beadle and Tatum Experiment (1941)Gene Concept : One gene One polypeptide
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The Griffith Experiment Discovery of Transformation
Griffith injected mice with various strains of bacteria
Streptococcus pneumoniae (known as pneumococcus)• Virulent, coated bacteria (Smooth form) lethal to
mice • Non-virulent, coatless strain (Rough form) not
lethal • Coat necessary for infection
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Wild type
Smooth, virulent
(IIIS)
Mutant type
Rough, non-virulent
(IIR)
Symbol of bacteria
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TRANSFORMATION (1931 F. GRIFFITH)
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Observation :
Conclusion: Living R cells are converted to S cells Transformation occurred
Question:• Was the “transforming agent” protein or DNA, or
what?
ControlsLiving S (smooth) cells + mouse = mouse deadLiving R (rough) cells + mouse = mouse healthy
Heat-killed S cells + mouse = mouse healthy
CombinationsHeat-killed S cells + Living R cells + mouse
= mouse dead
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-prove that the transforming principle is DNA
- Use purified DNA from types S (smooth) and was treated with:
* DNase : break down DNA* RNase : degrades RNA* Protease : degrades protein
The Avery et. al. Experiment
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Experiments carried out by Avery et. al.
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Conclusion:
The “transforming agent” was in fact DNA