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MOLECULAR GENETICS THE CHEMICAL NATURE OF THE GENE © 2007 Paul Billiet ODWSODWS
What does a gene do? The must be able to hold information and decode it (translate it) into an organism as it grows and develops It must be able to copy itself so that it can be passed on to future generations © 2007 Paul Billiet ODWSODWS
What does a gene look like? It must be a big molecule to hold the large amount of information required to build an organism It must be a complex molecule to provide the necessary variation to code the instructions that control growth and development © 2007 Paul Billiet ODWSODWS
Four classes of molecules which could form genes NucleotidesCHONPPolynucleotides (Nucleic acids) Amino acidsCHONSPolypeptides (proteins) Fatty acids (and glycerol) CHOLipids (Fats, oils and waxes) MonosaccharidesCHOPolysaccharides (carbohydrates) Building BlocksElementsBiological macromolecules © 2007 Paul Billiet ODWSODWS
Griffiths (1928) Tried to determine what genetic material was made of. National Library of Medicine's Profiles in Science © 2007 Paul Billiet ODWSODWS
Griffiths’ Experiment Pneumococcus bacteria on mice 2 STRAINS S-type Smooth colonies Virulent R-type Rough colonies Avirulent Innoculate into mice Dead from pneumonia Not killed © 2007 Paul Billiet ODWSODWS
Griffiths’ Experiment Live S-type found Further test: Cultured lung fluid No mice died Mice died from pneumonia CONTROL Heat-killed S-type only CONTROL Live R-type only EXPERIMENT Live R-type (harmless) + Heat-killed S-type © 2007 Paul Billiet ODWSODWS
Conclusion Transformation of R-type to S-type Transformation was brought about by some heat stable compound present in the dead S-type cells Called the TRANSFORMING PRINCIPLE © 2007 Paul Billiet ODWSODWS
Avery, MacCleod & McCarthy (1944) Tried purifying the transforming principle to change R-type Pneumococcus to S-type National Library of Medicine's Profiles in Science © 2007 Paul Billiet ODWSODWS
Results The compound that had the most effect was: Colourless, viscous and heat stable It contains phosphorus It was not affected by trypsin (a protease) or amylase. It was inhibited by RNAase and DNAase Conclusion The transforming principle is a nucleic acid © 2007 Paul Billiet ODWSODWS
Experiment Mice died from pneumonia Live R-type + DNA extracted and purified from S-type bacteria These S-type bacteria remained virulent for generation after generation Live S-type bacteria cultured from the lung fluid © 2007 Paul Billiet ODWSODWS
Conclusion DNA is the transforming principle and it is hereditary material Criticism The DNA was not totally pure It was contaminated by a small amount of protein This protein could be the real transforming principle BUT When Avery and his team prepared purer extracts of DNA they became better at transforming the bacteria types © 2007 Paul Billiet ODWSODWS
MOLECULAR GENETICS THE CHEMICAL NATURE OF THE GENE.
Chapter 12 DNA: The Genetic Material Identification of the Genetic Material (DNA) In 1928, an experiment unrelated to genetics led to the discovery of.
More from Chapters 1928 – Frederick Griffith is trying to develop a vaccine for Streptococcus pneumoniae, which causes pneumonia Griffith was.
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Section * 1928 British scientist – Frederick Griffith * Wanted to know how bacteria made people sick, especially pneumonia * Griffith isolated 2.
10.1 DNA: The Hereditary Material
Introduction to DNA (Deoxyribonucleic acid). Questions at the beginning of the 20th Century How do genes work? What are they made of, and how do they.
Copyright Pearson Prentice Hall. Griffith and Transformation 1928, British scientist Fredrick Griffith was trying to learn how certain types of bacteria.
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12.1: Identifying the Substance of Genes. Investigating bacteria and pneumonia S strain: mouse dies of pneumonia R strain: mouse lives Heat-killed.
How do we know DNA is the genetic material 12-1 DNA.
1 Review List the conclusions that Griffith and Avery drew from their experiments Identify Variables What experimental variable did Avery use when he.
Identifying the Substance of Genes
Objectives 12.1 Identifying the Substance of Genes -Summarize the process of bacterial transformation. -Describe the role of bacteriophages in identifying.
Born: October 21, 1877 Died: 2 February 1955 Nationality: Canadian Known for: DNA transmits heredity.
12.1 Identifying the Substance of Genes
BELLRINGER 1/21 Copy and complete the complementary strand of DNA on a ½ sheet of paper, 1-6: G T A C C T 1. _ 2. _ 3. _ 4. _ 5. _ 6. _.
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Chapter 12: DNA and RNA. Genes are made of DNA, a large, complex molecule. DNA is composed of individual units called nucleotides. Three of these units.
DNA: The Information Molecule How did scientists use evidence to discover that the DNA molecule contains information?
Chapter 12 DNA. Section 12.1 Identifying the Subsrance of Gene Summarize the process of bacterial transformation. Describe the role of bacterio- phages.
Copyright Pearson Prentice Hall
Nucleic Acids DNA & RNA. Where did we find Genes and who Discovered Them? In 1928 a man named Frederick Griffith was trying to figure out how bacteria.
Lecture 12 DNA Replication Molecular Biology of the Gene.
The Discovery of DNA. The DNA Revolution In 1928, Griffith discovered that a factor in heat-killed, disease causing bacteria can “ transform” harmless.
Biology 9.1 Identifying Genetic Material
DNA: Deoxyribonucleic Acid. I. Molecule for Heredity A. Scientists needed a molecule that could carry 3 main functions: 1. Carry genes from generation.
End Show Slide 1 of 37 Copyright Pearson Prentice Hall Biology.
CHAPTER 9.1 Identifying the Genetic Material Grade 10 Biology Spring 2011.
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Interest Grabber Order! Order! Genes are made of DNA, a large, complex molecule. DNA is composed of individual units called nucleotides. Three of these.
DNA. 12–1 DNA Griffith and Transformation I Griffith and Transformation In 1928, British scientist Fredrick Griffith was trying to learn how certain.
Chapter 8: DNA and RNA Section 8-1: Discovering DNA.
Chapter 12 DNA and RNA.
History of DNA structure and its importance How did we learn that DNA is the key to coding for all characteristics of living things?
End Show Slide 1 of 37 Copyright Pearson Prentice Hall 12–1 DNA.
8.1 Identifying DNA as the Genetic Material
Slide 1 of 37 Copyright Pearson Prentice Hall Biology.
Mendel’s Experiments Gregor Mendel was an Austrian monk who conducted experiments on pea plants Mendel’s experiments answered many questions, but.
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