RNA World Hypothesis Objectives 1 Be able to

RNA World Hypothesis Objectives: 1. Be able to Summarize the Miller-Urey Experiment 2. Relate the structure of Clay beds to the polymerization of nucleotides 3. Understand the role of meteorite impacts in polymerization of Proteins 4. Relate the structure of phospho-lipids to the formation of cell membranes.

Two Characteristics of a Living Thing

Must be able to store information (RNA or DNA)

Express that information (proteins) Actin /Mysosin: Proteins that are used in muscle fibers. Collagen: Found in connective tissue PSD-95: Protein that builds connections between synapses Proteases: Protiens that help digest proteins (meat) Keratin: A hard durable protein found in Hair and Nails/Claws

What came first The protein that makes up our body, or the RNA/DNA that codes for the protein?

Conditions of the Early Earth • Little oxygen in the atmosphere: Atmosphere is composed of CN, NH 4, CH 4, H 2 • Violent electrical storms • Heavy Bombardment: A time when the earth is constantly hit with meteorites.

Miller-Urey Experiment • Adds early atmospheric gases to a flask connected to another flask with water (simulating the early oceans). • Shot electrodes (simulate lightning) through the gases. • Produced amino acids (building blocks of Proteins) from the gases.

The Murchinson Meteorite • In 1969 a meorite hit earth in Australia • The meteorite was covered in thousands of amino acids, the building block of proteins. • Panspermian hypothesis: that life actually originated in space and was brought to this planet.

Experiments with Amino Acids under large impact pressures • Scientist hypothesized that if amino acids were placed under meteorite impact pressure, Dr. then Jennifer they Blank would vaporize. • The hypothesis was proved wrong: Amino acids Polymerized into long chains of protein.

The Formation of Nucleotides • Each of the 4 Nucleotides found in DNA: Adenine, Thymine, Cytosine, and Guanine have been synthesized in the laboratory using early atmospheric gases and an electrical discharge.

Polymerization of Nucleotides into Nucleic Acids • Polymerization: to attach smaller building blocks into long chains

Clay beds may have polymerized Nucleotides into long chains A T C G A C G

Evidence for Clay Beds • Many Organic Molecules are Chiral (mirror images), and come in two different isomers, either left-handed and right handed. • Clay beds only polymerize the L-isomer of nucleotides. • The L-isomer is the only form that nucleotides are found in living organisms.

Ribozymes • Ribozyme: A sequence of RNA (nucleic acid) that can catalyze chemical reaction. • It can act as both a heritary molecule (store information) and performs a function (expresses that information). • Biologist have discovered a Ribozyme that can catalyze its own synthesis.

• Some of these Ribozymes would have been enclosed and protected in a lipid by-layer, creating the first living cell.

Natural Selection on the Molecular Level • Once the first molecule of RNA began to selfreplicate Natural Selection can go to work. • Sequences that were more efficient at selfreplicating increased in population.

• Walter Gilbert proposed that the cell used RNA as both the genetic material and the catalytic molecule, rather than dividing these functions between DNA and protein as they are today. • This hypothesis became known as the " RNA world hypothesis” of the origin of life.

Essay Question on the Exam You meet a man named bob who notices you studying your biology Cornell notes. “Oh” say Bob, “ I’ve always wondered how life came to be covering our planet. ” Explain to Bob the RNA world hypothesis.