What is RNA Hypothesis world? Lecture no. 2

Biochemical 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 . Lecture no. 2

The evolution of the ribosome In a new study, scientists compared three-dimensional structures of ribosomes from a variety of species of varying biological complexity, including humans, yeast, bacteria and archaea. The researchers found distinct fingerprints in the ribosomes where new structures were added to the ribosomal surface without altering the pre-existing ribosomal core, which originated over 3 billion years ago before the last universal common ancestor (LUCA) of life.  Credit: Loren Williams/Georgia Institute of Technology. Lecture no. 2

DNA is the genetic material Today, even schoolchildren have heard of DNA, and scientists routinely manipulate DNA in the laboratory. Early in the 20th century, however, identifying the molecules of inheritance loomed as a major challenge to biologists.

Life on Earth Probably Began with RNA 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. RNA might act as genetic material (in some viruses). Also, could really act as functional material (i.e., ribozymes) Lecture no. 2

The 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. RNA is the only currently used macromolecule that is both a carrier of genetic information and an enzyme. Lecture no. 2

Four more-recent lines of evidence have added much breadth and depth to the plausibility of the proposal 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. Lecture no. 2

Possible remnants of the RNA World 2 1 Rnase P- ribozyme that cleaves tRNA precursors Self-splicing introns Possible remnants of the RNA World Like DNA, RNA can store and replicate genetic information; like enzymes, it can catalyze (start or accelerate) chemical reactions that are critical for life (then called Ribozyme).[7] One of the most critical components of the cell, ribosome, is composed primarily of RNA. Ribonucleotide moieties in many coenzymes, such as Acetyl-CoA, NADH, FADH and F420, have long been thought to be surviving remnants of covalently bound coenzymes in an RNA world.[ 3 4 5 Self-cleaving viral RNAs Peptidyl transferase in the ribosome Nucleotides (ribo) involved in metabolism, Signalling..etc Lecture no. 2

Research in different fields is coming together to assemble a more complete picture of the way the RNA World began and operated. a | Progress in organic chemistry helps to show how nucleotides and RNA oligomers could have been synthesized before life. b | In vitro evolution studies discover functional ribozymes in the very large RNA sequence space. c | Theoretical models emphasize the importance of stochasticity and spatial structure for the evolution of replicators. d | Both experiment and theory point to the different ways in which molecular cooperation is essential. e | The way that a free energy source can drive RNA synthesis and replication is still poorly understood. f | Synthesis of ribozymes that operate under different conditions gives some clues as to what the early Earth environment might have been like. g | Experiments on linking RNA replication with vesicle growth and division are moving towards the creation of artificial cells. Lecture no. 2

“The century of biology upon which we are now well embarked is not matter of trivialities. It is movement of really heroic dimensions, one of the great episodes in man’s intellectual history. Do not be fooled into thinking this is mere gadgetry. This is the understanding of life.” Warren Weaver Lecture no. 2

Characteristics of the genetic material For a molecule to serve as the genetic material, it must be It must be a in a stable form containing information about cell structure and function. It must able to replicate accurately. It must be capable of being expressed when needed.

Molecular 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. Gregor Mendel’s (1865) Three Laws of Inheritance Friedrich Miescher (1869) identified DNA & called it nuclein Lecture no. 2

Mendel's Laws of Heredity are usually stated as: 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. Lecture no. 2

Continue… 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. Lecture no. 2

Continue… The Law of Dominance: An organism with alternate forms of a gene will express the form that is dominant. Lecture no. 2

Thomas H. Morgan (1910) discovers genes on chromosomes Beadle & Tatum (1941) One gene-one enzyme Lecture no. 2

Avery, Mcleod & McCarty (1944) DNA is genetic material Lecture no. 2 17

Edwin Chargaff (1950) find C complements G and A complements T Watson, Crick, Franklin, Wilkins (1953) Structure of DNA Lecture no. 2 18 18

Brenner, Jacob & Meseleson (1961) Discovery of mRNA Lecture no. 2 19 19 19

Central Dogma; Crick & Gamov 1956 Central Dogma; Crick & Gamov 1966 Finished unraveling the code; Nirenberg & Khorana 1972 Recombinant DNA made in vitro; P. Berg 1973 DNA cloned on a plasmid; H. Boyer & S. Cohen 1973 Discovery of reverse transcriptase; H. Temin Lecture no. 2

Rapid DNA sequencing; F. Sanger & W. Gilbert Lecture no. 2 1977 Rapid DNA sequencing; F. Sanger & W. Gilbert 1977 Discovery of split genes; Sharp, Roberts et al. 1982 Discovery of ribozymes; T. Cech & S. Altman 1986 Creation of PCR; K. Mullis et al. Lecture no. 2

Human Genome Project The Human Genome Project (HGP) began in October 1990 and completed in 2003, with a primary goals of : identify all the approximately 20,500 genes in human DNA, determine the sequences of the 3 billion chemical base pairs that make up human DNA, store this information in databases, improve tools for data analysis, transfer related technologies to the private sector, and address the ethical, legal, and social issues (ELSI) that may arise from the project. Though the HGP is finished, analyses of the data will continue for many years. Lecture no. 2

Timeline of the Human Genome Project, 1990 - 2003 https://www.mun.ca/biology/scarr/Human_Genome_Project_timeline.html

“We are in the midst of a "Golden Era" of biology, and the revolution is mostly about treating biology as an information science, and not only as specific biochemical technologies” Lecture no. 2

For more information please visit the following link: http://www.dnai.org/timeline/index.html Lecture no. 2

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. Lecture no. 2