I. To understand Genetics - A. Chemical nature of genes had to be discovered B. Allow us to understand how genes control inherited characteristics

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1 Ch 12 Lecture Notes - DNA I. To understand Genetics - A. Chemical nature of genes had to be discovered B. Allow us to understand how genes control inherited characteristics 1 II. Griffith and Transformation A. Griffith was not looking for chemical nature of genes instead he was trying to find out how pneumonia was caused. B. Griffith s experiment 1. Two strains of pneumonia bacteria a. rough - harmless b. smooth - disease causing 2. Injected mice with both strains a. rough strain - mice lived b. smooth strain - mice died - no surprise Was a poison produced to kill the mice? 3. Then - heat killed, disease causing smooth strain injected into mice - mice lived Conclusion I: pneumonia is not caused by a poison. 4. Then- mixed heat killed with rough - injected into mice - mice died - Unexpected **Conclusion II: Heat killed passed disease causing to harmless - transformation - changed harmless bacteria into disease causing bacteria Trace page text

2 III. Avery and DNA 2 A. Repeated Griffith s work - which molecule was transferred? B. Treated heat-killed bacteria with enzymes to destroy all molecules that made up the bacteria - Transformation still occurred. Conclusion: Obviously not all molecules were destroyed. C. Repeated experiment except used enzymes that would destroy DNA - No transformation occurred. **Conclusion: DNA is the molecule that stores and transmits genetic information. IV. Hershey - Chase - concluded, finally, that DNA contained the genetic material - genes. Also concluded that DNA was not a protein. A. Used bacteriophages (virus) Protein coat - marker S radioactive sulfur DNA - marker P radioactive phosphorus B. bacteriophage inject contents into bacterium, then separated viruses from bacteria 32 C. All bacteria contained P - the DNA marker **Conclusion: Genetic material was DNA Trace page text

3 V. Structure of DNA 3 A. Made of units called nucleotides 1. Sugar called Deoxyribose 2. Phosphate group 3. Nitrogenous base Purines - single ring structure a. Adenine b. Guanine Pyrimidines - two ring structure c. Thymine d. Cytosine B. Backbone of DNA chain is sugar and phosphorus C. Bases stick out like rungs of a ladder D. Double helix - twisted ladder Trace and label figure 12-7 page 294 E. Base pairings = A- T G - C VI. DNA and Chromosomes A. Prokaryotes have a single circular chromosome that contains all of the DNA B. Eukaryotes have 100's or even 1,000's of times more DNA

4 1. DNA is enclosed in a nucleus 4 2. DNA is folded so more will fit in the nucleus 3. DNA is coiled and tightly packed - Histomes help to pack DNA Trace and label Fig page 297 VII. DNA Replication - making an exact copy - DNA molecule unzips, exposing the two strands of DNA. Following the rules of base pairings, make two new strands of DNA. Each strand of the double helix serves as a template or model for the new DNA strand. Trace and label fig12-11 page 298 IX. From DNA to Protein A. Structure of RNA 1. single stranded 2. uracil, not thymine B. Types of RNA - three types 1. mrna - messenger RNA - get the message from the DNA template 2. rrna - ribosomal RNA - in the

5 ribosome where the message is 5 translated 3. trna - transfer RNA - makes polypeptide chains (proteins) of amino acids according to the mrna code. C. Translation - DNA to mrna 1. requires RNA polymerase 2. RNA polymerase unzips DNA to reveal the code (template) 3. mrna is assembled according to the base pair coding 4. transcribed mrna is now ready for translation 5. promoters in the DNA sequence tell the mrna where to begin and end. D. RNA Editing - sometimes mistakes are made 1. introns are large pieces of RNA molecule that have been cut out of the first rough draft 2. Exons are RNA spliced back together to make the final copy

6 E. Genetic Code 6 1. proteins are made by joining amino acids in a chain (polypeptide chain) 2. only twenty amino acids - thousands of proteins 3. each amino acid is coded by a sequence of three bases called a codon 4. some amino acids are coded by more than one codon Trace and label fig p. 303 F. Translation - mrna is run through a ribosome where trna uses the code to make a polypeptide chain. G. Events Summary - 1. DNA to mrna in nucleus - transcription 2. mrna to ribosome - trna translates code and releases an amino acid to make a polypeptide chain. Trace and label fig p

7 H. Why is it so important for proteins 7 (polypeptide chains) to be made? 1. a gene that codes for an enzyme (protein) will control what that protein is suppose to do. a. color of a flower, etc b. red blood cell, etc 2. proteins are the key to all living things X. Mutations - changes in the DNA sequence A. Point mutations - affects one nucleotide - usually not a problem - affects only one gene B. Frame Shift mutation - addition or deletion of a 6 nucleotide and changes the reading frame - usually very serious - changes the function of the protein. Trace and label fig p. 307 C. Chromosomal mutation - change in the whole chromosome Trace and label Fig p. 308

8 XI. Gene Regulation - How the cell turns on 8 and off genes? A Certain DNA sequences serve as Promoters which is a binding site for RNA polymerase. B. Some DNA sequences serve as Start and stop signals C. Gene Regulation in Bacteria 1. Operon = group of genes that operate together 2. Operon is turned on and off by a repressor 3. Promoter is beginning point for mrna transcription and at the end is a stop codon. Trace and label Fig p The whole chromosome is expressed at the same time D. Gene Regulation in Eukaryotes 1. TATA box begins mrna transcription

9 2. Only parts of the chromosome are 9 expressed at any one time 3. Cell specialization requires genetic specialization E. Regulation and Development 1. Gene regulation shapes the complexity of development 2. Hox genes are a series of genes that controls tissues ans organs of an organism 3. A mutation of these hox genes (master genes) can cause complete change in body parts 4. Research with genes has also shown new sequences that cause normalcy in otherwise diseased or genetically altered conditions. stem cell research 5. What makes this possible? All genes in all organisms have the same common patterns of inheritance. All life on earth is related.