Section 7.1 Hypothesis Testing: Hypothesis: Null Hypothesis (H 0 ): Alternative Hypothesis (H 1 ):
RNA Hypothesis
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Transcript of RNA Hypothesis
RNA HypothesisRNA Hypothesis
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Life on Earth Probably Began with RNALife on Earth Probably Began with RNA
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• Living systems have definable characteristics and requirements. Catalysis and biological information are particularly important requirements for any life form.
• The first molecule that fulfilled the requirements of catalysis and biological information may have been a self-replicating RNA, according to the RNA world hypothesis.
The RNA WorldThe RNA World• The RNA world hypothesis was first
proposed as a stage in evolution. The hypothesis describes a living system (or set of living systems) based on RNA.
• In this system, a variety of RNA enzymes could catalyze all of the reactions needed to synthesize the molecules required for life from simpler molecules available in the environment.
• The “RNA organism,” out of equilibrium with its surroundings, would have to be defined by a boundary.
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RNA is the only RNA is the only currently used currently used macromoleculemacromoleculethat is both a carrier of that is both a carrier of genetic information andgenetic information andan enzyme.an enzyme.
Four more-recent lines of evidence have added much breadth and depth to the plausibility of the
proposal
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• The first was the discovery (early 1980s) of catalytic RNAs, or ribozymes- enzymes that are made of RNA instead of protein.
• The second and third discoveries that in ribosomes, the large ribonucleoprotein complexes that translate RNA into protein, the RNA is the active component with the capacity to catalyze protein synthesis.
• Another supportive research demonstrated that artificially constructed RNA molecules can catalyze almost any imaginable reaction needed in a living system.
• Finally, and most recently, RNA sequences capable of simple forms of self-replication have been discovered.
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Possible remnants of the RNA Possible remnants of the RNA WorldWorld
Self-splicing introns
Rnase P- ribozyme that cleaves tRNA
precursors
Self-cleaving viral RNAs
Peptidyl transferase in the ribosome
Nucleotides (ribo) involved in metabolism, Signalling..etc
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Biochemical Unity Underlies Biological DiversityBiochemical Unity Underlies Biological Diversity
LUCA, the last universal common ancestor of all life now present on earth, can be studies by identifying the common characteristics of living organisms and defining the minimal complement of genes necessary to support a living cell.
On the basis of their biochemical characteristics, the diverse organisms of the modern world can be divided into three fundamental groups called domains: Eukarya (eukaryotes), Bacteria, and Archaea .
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The universal tree of life. A current version of the tree is shown, with branches for the three main groups of known organisms: bacteria, archaea, and eukaryotes.
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The Modern Era: The Impact of Molecular The Modern Era: The Impact of Molecular BiologyBiology
The molecular biology revolution in the middle of the Twentieth Century provided the means to study the role of genes in development.
The key technological advance for the study of gene control of development was the ability to isolate and clone genes.
The patterns of expression of individual genes could be followed by tracing the products of their expression.
Molecular biology obtained a very powerful tool to facilitate the study of nucleic acids when the polymerase chain reaction (PCR) was developed, which amplify specific sequences of DNA many-fold from a minute amount of starting material.
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Molecular Biology TimelineMolecular Biology Timeline
The term molecular biology first appeared in mid 1800s in a report prepared for the Rockefeller Foundation by Warren Weaver.
Two studies performed in the 1860s provided the foundation for molecular biology.
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Gregor Mendel’s (Gregor Mendel’s (18651865) Three Laws of ) Three Laws of InheritanceInheritance
Friedrich Miescher (Friedrich Miescher (18691869) identified DNA & called it ) identified DNA & called it nucleinnuclein
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Mendel's Laws of Heredity are usually stated as:
1) The Law of Segregation: Each inherited trait is defined by a gene pair. Parental genes are randomly separated to the sex cells so that sex cells contain only one gene of the pair. Offspring therefore inherit one genetic allele from each parent when sex cells unite in fertilization.
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2) The Law of Independent Assortment: Genes for different traits are sorted separately from one another so that the inheritance of one trait is not dependent on the inheritance of another.
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3) The Law of Dominance: An organism with alternate forms of a gene will express the form that is dominant.
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Thomas H. Morgan (Thomas H. Morgan (19101910) discovers genes on ) discovers genes on chromosomeschromosomes
Beadle & TatumBeadle & Tatum ( (19411941) ) One gene-one One gene-one enzymeenzyme
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Avery, Mcleod & McCarty ((19441944) ) DNA is genetic material
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Watson, Crick, Franklin, Wilkins((19531953) ) Structure of DNA
Edwin Chargaff ((19501950) ) find C complements G and A complements T
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Brenner, Jacob & Meseleson ((19611961) ) Discovery of mRNA
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Central Dogma; Crick & Gamov
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Recombinant DNA made in vitro; P. Berg
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DNA cloned on a plasmid; H. Boyer & S. Cohen
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Discovery of reverse transcriptase; H. Temin
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Finished unraveling the code; Nirenberg & Khorana
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Rapid DNA sequencing; F. Sanger & W. Gilbert
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Discovery of split genes; Sharp, Roberts et al.
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Discovery of ribozymes; T. Cech & S. Altman
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Creation of PCR; K. Mullis et al.
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Molecular Biology 2000- PresentMolecular Biology 2000- Present
2000- The fly Drosophila melanogaster is one of the most intensively studied organisms in
biology and serves as a model system for the investigation of many developmental and cellular
processes common to higher eukaryotes, including humans. Scientists have determined the
nucleotide sequence of nearly all of the approximately 120-megabase euchromatic portion of
the Drosophila genome using a whole-genome shotgun sequencing strategy.
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The genome sequence of Drosophila melanogaster.
Science. 287:2185-95. 2000.
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2001- The Human Genome Project (HGP) began in October 1990 with a primary goal of determining the sequence of chemical base pairs which make up DNA, and of identifying and mapping the approximately 20,000–25,000 genes of the human genome from both a physical and functional standpoint.
Due to widespread international cooperation and advances in the field of genomics (especially in sequence analysis), as well as major advances in computing technology, a 'rough draft' of the genome was finished in 2000 (announced jointly by U.S. President Bill Clinton and the British Prime Minister Tony Blair on June 26, 2000).
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http://www.ornl.gov/sci/techresources/Human_Genome/home.shtml
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2003- The Human Genome Project (HGP). Mouse genome is sequenced.
2004- Rat genome sequenced.
2010- Understanding the function of all genes within their cellular, organismal and evolutionary context of Arabidopsis thaliana
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Nobel Prize Laureates in Nobel Prize Laureates in Physiology or Medicine from 2006 Physiology or Medicine from 2006
to present to present
2006 - ANDREW Z. FIRE, and CRAIG C. MELLO for their discovery of RNA interference - gene silencing by double-stranded RNA.
2007- MARIO R. CAPECCHI, SIR MARTIN J. EVANS, and OLIVER SMITHIES for their discoveries of principles for introducing specific gene modifications in mice by the use of embryonic stem cells.
2009- ELIZABETH H. BLACKBURN, CAROL W. GREIDER, and JACK W. SZOSTAK for the discovery of how chromosomes are protected by telomeres and the enzyme telomerase
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We are in the midst of a "Golden EraGolden Era" of biology,and the revolution is mostly about treating biology as an information science, and not only as specific biochemical technologies
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Homework:Can you identify the most important terms that you have gone through a lecture today and find a scientific definition for it.Remember this will be your next lecture, so be prepared.
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