12.1 The Genetic Material Objective: 6(A) Identify components of DNA, and describe how information for specifying the traits of an organism is carried in the DNA

6(A) Identify components of DNA, and describe how information for specifying the traits of an organism is carried in the DNA. 1(A) Demonstrate safe practices during laboratory and field investigations. 2(C) know scientific theories are based on natural and physical phenomena and are capable of being tested by multiple independent researchers. Unlike hypotheses, scientific theories are well-established and highly-reliable explanations, but they may be subject to change as new areas of science and new technologies are developed 3(A) In all fields of science, analyze, evaluate, and critique scientific explanations by using empirical evidence, logical reasoning, and experimental and observational testing, including examining all sides of scientific evidence of those scientific explanations, so as to encourage critical thinking by the student. Copyright © McGraw-Hill Education DNA: The Genetic Material

4(A) Compare and contrast prokaryotic and eukaryotic cells. 3(E) Evaluate models according to their limitations in representing biological objects or events. 3(F) Research and describe the history of biology and contributions of scientists 4(A) Compare and contrast prokaryotic and eukaryotic cells. 6(B) Recognize that components that make up the genetic code are common to all organisms. 9(D) Analyze and evaluate the evidence regarding formation of simple organic molecules and their organization into long complex molecules having information such as the DNA molecule for self-replicating life. Copyright © McGraw-Hill Education DNA: The Genetic Material

Essential Questions Which experiments led to the discovery of DNA as the genetic material? What is the basic structure of DNA? What is the basic structure of eukaryotic chromosomes? Copyright © McGraw-Hill Education DNA: The Genetic Material

Vocabulary Review New nucleic acid double helix nucleosome DNA: The Genetic Material Copyright © McGraw-Hill Education

Discovery of the Genetic Material After the rediscovery of Mendel’s work, scientist began to look for the molecule involved in inheritance. For many years, scientists struggled to determine if DNA or protein was the source of genetic information. Copyright © McGraw-Hill Education DNA: The Genetic Material

Discovery of the Genetic Material Griffith’s Experiment First major experiment searching for the genetic material. Involved transformation between two forms of S. pneumoniae Set the stage for the search to identify the transforming substance Copyright © McGraw-Hill Education DNA: The Genetic Material

Discovery of the Genetic Material Avery’s Work Identified the molecule that transformed the R strain of S. pneumoniae into the S strain Concluded that when the S cells were killed, DNA was released R bacteria incorporated this DNA into their cells and changed into S cells Copyright © McGraw-Hill Education DNA: The Genetic Material

Discovery of the Genetic Material Hershey and Chase’s Experiments Used radioactive labeling to trace bacteriophage DNA and protein. Concluded that the bacteriophage DNA was injected into the cell and provided the genetic information needed to produce new viruses. Copyright © McGraw-Hill Education DNA: The Genetic Material

DNA Structure Nucleotides Nucleotides are the subunits of nucleic acids, and consist of 5-carbon sugar Phosphate group Nitrogenous base Copyright © McGraw-Hill Education DNA: The Genetic Material

DNA Structure Chargaff Analyzed the amount of A, G, T, and C in the DNA of various species Chargaff’s rule: C = G and T = A Copyright © McGraw-Hill Education DNA: The Genetic Material

DNA Structure The structure question Search for the structure of DNA was lead by four scientists: Rosalind Franklin, British chemist Maurice Wilkins, British physicist Francis Crick, British physicist James Watson , American biologist Copyright © McGraw-Hill Education DNA: The Genetic Material

DNA Structure X-ray diffraction X-ray diffraction techniques indicated that DNA was a double helix, or twisted ladder shape. The double helix shape was formed by two strands of nucleotides twisted around each other. Copyright © McGraw-Hill Education DNA: The Genetic Material

DNA Structure Watson and Crick Using Franklin and Chargaff’s data, Watson and Crick measured the width of the helix and the spacing of the bases. They built a model that conformed the Franklin and Chargaff’s data. Copyright © McGraw-Hill Education DNA: The Genetic Material

DNA Structure DNA structure DNA often is compared to a twisted ladder. Rails of the ladder are represented by the alternating deoxyribose and phosphate. The pairs of bases (cytosine-guanine or thymine-adenine) form the steps. Purine base always binds to a pyrimidine base Copyright © McGraw-Hill Education DNA: The Genetic Material

DNA Structure Orientation DNA molecules have specific orientations of the two strands On the top rail, the strand is said to be oriented 5’ to 3’. The strand on the bottom runs in the opposite direction and is oriented 3’ to 5’. Copyright © McGraw-Hill Education DNA: The Genetic Material

Chromosome Structure In prokaryotes, DNA molecules are contained in the cytoplasm, and consist mainly of a ring of DNA and associated proteins. In eukaryotes, DNA is organized into individual chromosomes. Copyright © McGraw-Hill Education DNA: The Genetic Material

Chromosome Structure To fit into a cell, DNA coils around a group of beadlike proteins called histones. DNA + histones form a nucleosome, which group together into chromatin fibers, which supercoil to form a chromosome. Copyright © McGraw-Hill Education DNA: The Genetic Material

Review Essential Questions Vocabulary Which experiments led to the discovery of DNA as the genetic material? What is the basic structure of DNA? What is the basic structure of eukaryotic chromosomes? Vocabulary double helix nucleosome Copyright © McGraw-Hill Education DNA: The Genetic Material