4/22/2014. Interest Grabber. Section Outline. Today s Goal. Percentage of Bases in Four Organisms. Figure 12 2 Griffith s Experiment

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1 Order! Order! Genes are made of, a large, complex molecule. is composed of individual units called nucleotides. Three of these units form a code. The order, or sequence, of a code and the type of code determine the meaning of the message. 1. On a sheet of paper, write the word cats. List the letters or units that make up the word cats. 2. Try rearranging the units to form other words. Remember that each new word can have only three units. Write each word on your paper, and then add a definition for each word. 3. Did any of the codes you formed have the same meaning? 4. How do you think changing the order of the nucleotides in the codon changes the codon s message? 12 1 A. Griffith and Transformation 1. Griffith s Experiments 2. Transformation B. Avery and C. The Hershey-Chase Experiment 1. Bacteriophages 2. Radioactive Markers D. The Structure of 1. Chargaff s Rules 2. X-Ray Evidence 3. The Double Helix Percentage of Bases in Four Organisms Today s Goal Source of A T G C Streptococcus Yeast Herring Human Examine the experiments that led to our knowledge that carries genetic information. i.e. is responsible for passing on information Remember: Scientists understood that cells were made up of many organic molecules including proteins, carbohydrates, lipids, and nucleic acids. What they didn t know was which was responsible for carrying genetic information. Figure 12 2 Griffith s Experiment Figure 12 2 Griffith s Experiment Heat-killed, disease-causing Heat-killed, disease-causing Disease-causing Harmless bacteria Heat-killed, diseasecausing bacteria (smooth Control (no growth) Harmless bacteria Disease-causing Harmless bacteria Heat-killed, diseasecausing bacteria (smooth Control (no growth) Harmless bacteria Dies of pneumonia Lives Lives Live, disease-causing Dies of pneumonia Dies of pneumonia Lives Lives Live, disease-causing Dies of pneumonia 1

2 Figure 12 4 Hershey-Chase Experiment phosphorus-32 in Radioactivity inside sulfur-35 in protein coat No radioactivity inside Figure 12 4 Hershey-Chase Experiment Figure 12 4 Hershey-Chase Experiment phosphorus-32 in Radioactivity inside phosphorus-32 in Radioactivity inside sulfur-35 in protein coat No radioactivity inside sulfur-35 in protein coat No radioactivity inside Figure 12 5 Nucleotides Chargaff s Rule Base Pairing Rule Purines Pyrimidines Adenine Guanine Cytosine Thymine Source of A T G C Streptococcus Yeast Herring Human Phosphate group Deoxyribose % of A % of T % of G % of C 2

3 Rosalind Franklin X Ray diffraction Watson and Crick Model 1. Shaped is twisted 2. Contain two strands Figure 12 7 Structure of Prokayrotic vs. Eukaryotic Nucleotide Hydrogen bonds Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G) Prokaryotic Chromosome Structure How is packaged Chromosome E. coli Bases on the chromosome 3

4 Figure Chromosome Structure of Eukaryotes Human cells contain over one meter of! How? Chromosome Nucleosome Supercoils Coils double helix A Perfect Copy When a cell divides, each daughter cell receives a complete set of chromosomes. This means that each new cell has a complete set of the code. Before a cell can divide, the must be copied so that there are two sets ready to be distributed to the new cells. Histones Wrapped around proteins (histones and nucleosomes) continued 1. On a sheet of paper, draw a curving or zig-zagging line that divides the paper into two halves. Vary the bends in the line as you draw it. Without tracing, copy the line on a second sheet of paper. 2. Hold the papers side by side, and compare the lines. Do they look the same? 3. Now, stack the papers, one on top of the other, and hold the papers up to the light. Are the lines the same? 4. How could you use the original paper to draw exact copies of the line without tracing it? 5. Why is it important that the copies of that are given to new daughter cells be exact copies of the original? 12 2 Chromosomes and Replication A. and Chromosomes 1. Length 2. Chromosome Structure B. Replication 1. Duplicating 2. How Replication Occurs Figure Replication New strand Original strand polymerase replication Growth polymerase Growth Replication fork Replication fork Nitrogenous bases New strand Original strand 4

5 Information, Please contains the information that a cell needs to carry out all of its functions. In a way, is like the cell s encyclopedia. Suppose that you go to the library to do research for a science project. You find the information in an encyclopedia. You go to the desk to sign out the book, but the librarian informs you that this book is for reference only and may not be taken out. 1. Why do you think the library holds some books for reference only? 2. If you can t borrow a book, how can you take home the information in it? 3. All of the parts of a cell are controlled by the information in, yet does not leave the nucleus. How do you think the information in might get from the nucleus to the rest of the cell? 12 3 RNA and Protein Synthesis A. The Structure of RNA B. Types of RNA C. Transcription D. RNA Editing E. The Genetic Code F. Translation G. The Roles of RNA and H. Genes and Proteins RNA vs. Concept Map RNA can be Messenger RNA Transfer RNA also called which functions to also called which functions to mrna Carry instructions trna Bring amino acids to ribosome from to Figure Transcription Figure The Genetic Code Adenine ( and RNA) Cystosine ( and RNA) Guanine( and RNA) Thymine ( only) Uracil (RNA only) RNA polymerase RNA 5

6 Figure Translation Figure Translation (continued) Messenger RNA Messenger RNA is transcribed in the nucleus. Phenylalanine trna Methionine Nucleus Lysine mrna Transfer RNA The mrna then enters the cytoplasm and attaches to a ribosome. Translation begins at AUG, the start codon. Each transfer RNA has an anticodon whose bases are complementary to a codon on the mrna strand. The ribosome positions the start codon to attract its anticodon, which is part of the trna that binds methionine. The ribosome also binds the next codon and its anticodon. The Polypeptide Assembly Line The ribosome joins the two amino acids methionine and phenylalanine and breaks the bond between methionine and its trna. The trna floats away, allowing the ribosome to bind to another trna. The ribosome moves along the mrna, binding new trna molecules and amino acids. Lysine trna trna mrna Growing polypeptide chain Completing the Polypeptide mrna Start codon mrna Translation direction The process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain. Protein Synthesis - Start to finish Determining the Sequence of a Gene contains the code of instructions for cells. Sometimes, an error occurs when the code is copied. Such errors are called mutations. continued 1. Copy the following information about Protein X: Methionine Phenylalanine Tryptophan Asparagine Isoleucine STOP. 2. Use Figure on page 303 in your textbook to determine one possible sequence of RNA to code for this information. Write this code below the description of Protein X. Below this, write the code that would produce this RNA sequence. 3. Now, cause a mutation in the gene sequence that you just determined by deleting the fourth base in the sequence. Write this new sequence. 4. Write the new RNA sequence that would be produced. Below that, write the amino acid sequence that would result from this mutation in your gene. Call this Protein Y. 5. Did this single deletion cause much change in your protein? Explain your answer Mutations A. Gene Mutations B. Chromosomal Mutations 6

7 Gene Mutations: Substitution, Insertion, and Deletion Figure Chromosomal Mutations Deletion Substitution Insertion Deletion Duplication Inversion Translocation continued Regulation of Protein Synthesis Every cell in your body, with the exception of gametes, or sex cells, contains a complete copy of your. Why, then, are some cells nerve cells with dendrites and axons, while others are red blood cells that have lost their nuclei and are packed with hemoglobin? Why are cells so different in structure and function? If the characteristics of a cell depend upon the proteins that are synthesized, what does this tell you about protein synthesis? Work with a partner to discuss and answer the questions that follow. 1. Do you think that cells produce all the proteins for which the (genes) code? Why or why not? How do the proteins made affect the type and function of cells? 2. Consider what you now know about genes and protein synthesis. What might be some ways that a cell has control over the proteins it produces? 3. What type(s) of organic compounds are most likely the ones that help to regulate protein synthesis? Justify your answer. Typical Gene Structure Regulatory sites Promoter (RNA polymerase binding site) strand 12 5 Gene Regulation A. Gene Regulation: An Example B. Eukaryotic Gene Regulation C. Regulation and Development Start transcription Stop transcription 7