Interest Grabber Section Outline 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 Components and Structure of 1. Chargaff s Rules 2. X-Ray Evidence 3. The Double Helix Figure 12 2 Griffith s Experiment Frederick Griffith (1928) Did experiment to figure out how bacteria made people sick, in particular pneumonia. He isolated two different strains of pneumonia bacteria from mice. Only one of the strains caused the disease and grew into smooth colonies on culture plates. The other strain produced colonies that had rough edges. Griffith injected the mice with the different strains and these were the results. Harmless bacteria Control Disease-causing Heat-killed, disease (rough colonies) (no growth) bacteria (smooth -causing bacteria colonies) (smooth colonies) Dies of pneumonia Lives Lives Live, disease-causing bacteria (smooth colonies) Heat-killed, disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Dies of pneumonia Figure 12 2 Griffith s Experiment Transformation Disease-causing bacteria (smooth colonies) Harmless bacteria Heat-killed, disease (rough colonies) -causing bacteria (smooth colonies) Control (no growth) Heat-killed, disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) When Griffith mixed the heat-killed bacteria with the harmless bacteria the mice developed pneumonia. After an examination of the mice s lungs, Griffith found the disease-causing bacteria. Somehow, the disease-causing bacteria passed on their disease-causing ability to the harmless strain. Griffith called this process Transformation, because one strain permanently changed into the other strain. Dies of pneumonia Lives Lives Live, disease-causing bacteria (smooth colonies) Dies of pneumonia 1
Oswald Avery (1944) Oswald and his crew from the Rockefeller Institute in New York repeated Griffiths experiment. This time they used enzymes to kill any proteins, lipids, carbohydrates, and RNA. Transformation still occurred. Next, they used enzymes that broke down. Transformation did not occur. Avery and other scientists discovered that the nucleic acid,, stores and transmits the genetic information from one generation of an organism to the next. The Hershey-Chase Experiment Alfred Hershey and Martha Chase studied viruses, nonliving particles smaller than a cell that can infect living organisms. They focused on viruses that infect bacteria. They are known as Bacteriophages. They are composed of a or RNA core and a protein coat. Figure 12 4 Hershey-Chase Experiment Bacteriophage 1. The virus attaches to the surface of the cell and injects it genetic information. 2. The viral genes reproduce many new bateriophages inside the cell. 3. They gradually destroy the cell. 4. When the cell bursts open, all the new viruses are released. 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 2
Figure 12 5 Nucleotides The Components and Structure of = Deoxyribonucleic Acid is a long molecule made up of smaller units called nucleotides. Nucleotides are made up of three parts: 1. 5-carbon sugar (deoxyribose) 2. Phosphate group 3. Nitrogen base Two types of bases: Purines (two rings) Pyrimidines (One ring) 1. Adenine 1. Thymine 2. Guanine 2. Cytosine Nitrogen Base Purines Pyrimidines Adenine Guanine Cytosine Thymine Phosphate group Deoxyribose Percentage of Bases in Four Organisms Chargaff s Rule Chargaff discovered that the percentages of guanine and cytosine bases were almost equal in any sample of. The same was true for adenine and thymine. As a result A = T and C = G. Source of A T G C Streptococcus 29.8 31.6 20.5 18.0 Yeast 31.3 32.9 18.7 17.1 Herring 27.827.522.2 22.6 Human 30.9 29.4 19.9 19.8 X-Ray Evidence In the early 1950 s, Rosalind Franklin used X-ray diffraction to get information about the structure of. She shot a high power X-ray beam at a concentrated sample. The results showed an X shaped pattern that shows the strands are twisted around each other like a coil in a spring. This shape is called a helix. The Double Helix Francis Crick, a British physicist, and James Watson, an American biologist, were trying to understand the structure of. They tried to build a 3-D model using cardboard and wire, but were unable to get is right. When they saw the picture from Franklin, Watson got an idea and produced a model that is similar to what we know today. Watson and Crick s model of was a double helix, in which two strands were wound around each other. 3
The Double Helix A double helix looks like a twisted ladder or a spiral staircase. The frame is made up of the 5-carbon sugar and the phosphate group. The rungs or stairs were made up of the nitrogen bases. The two strands were held together by special bonds, hydrogen bonds. The hydrogen bonds could only form between certain bases. Adenine can only bond to Thymine and Cytosine could only bond to Guanine. This proved Chargoff s rule that for every adenine there was one thymine and the same for cytosine and guanine. Figure 12 7 Structure of Interest Grabber Nucleotide Hydrogen bonds A Perfect Copy Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G) 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. Interest Grabber continued Section Outline 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 4
Prokaryotic Chromosome Structure Chromosome Structure Prokaryotes lack nuclei, so their is found in the cytoplasm. Eukaryotic is 1,000 times longer than bacteria. Eukaryotic chromosomes contain that is tightly wrapped around a protein, called histone, to form a substance called chromatin. Chromosome E. coli E. coli - Contains 4,639,221 base pairs Bases on the chromosome Figure 12-10 Chromosome Structure of Eukaryotes Replication Chromosome Supercoils Nucleosome Coils Histones double helix In order for replication to occur, must uncoil from the histones. Once uncoiled, the polymerase attaches to separating, or unzipping, the two strands. Free floating nucleotides found in the nucleus will pair up to their complimentary base on the original strand. Replication will occur in both directions until two new strands are formed. Figure 12 11 Replication Interest Grabber New strand Original strand polymerase Information, Please polymerase Growth Growth 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? Replication fork New strand Replication fork Original strand Nitrogenous bases 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? 5
Section Outline Structure of RNA 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 (Ribonucleic Acid) differs from in 3 ways: 1. RNA is made up of a single strand of nucleotides 2. RNA contains the sugar Ribose. 3. The nitrogenous base uracil takes the place of thymine Types of RNA Concept Map There are three types of RNA RNA 1. Messenger RNA (mrna) - Carries information from to the ribosome to build proteins. 2. Ribosomal RNA (rrna) -Combines with proteins to make up a ribosome 3. Transfer RNA (trna) - Transfers a specific amino acid to the ribosome. can be Messenger RNA Ribosomal RNA Transfer RNA also called which functions to also called which functions to also called which functions to mrna Carry instructions rrna Combine with proteins trna Bring amino acids to ribosome from to to make up Ribosome Ribosomes Figure 12 14 Transcription Transcription Adenine ( and RNA) Cystosine ( and RNA) Guanine( and RNA) Thymine ( only) Uracil (RNA only) RNA polymerase RNA Transcription begins when the separates and RNA Polymerase binds to the promoter on one of the unzipped strands. Free floating RNA nucleotides will bond to their complimentary bases on the. Transcription continues until RNA Polymerase reaches a stop code. The mrna releases from the strand, leaves the nucleus, and the goes back to normal. 6
The Genetic Code Figure 12 17 The Genetic Code mrna contains all the information needed to make proteins. Every three consecutive bases makes up the code for the amino acids in the protein. This is called a codon. Figure 12 18 Translation Figure 12 18 Translation (continued) Section 12-4 Gene Mutations: Substitution, Insertion, and Deletion Section 12-4 Figure 12 20 Chromosomal Mutations Deletion Substitution Insertion Deletion Duplication Inversion Translocation 7
Interest Grabber Interest Grabber continued Section 12-4 Section 12-4 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. 1. Copy the following information about Protein X: Methionine Phenylalanin e Tryptophan Asparagine Isoleucine STOP. 2. Use Figure 12 17 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. Section 12-4 Section Outline Section 12-5 Interest Grabber Regulation of Protein Synthesis 12 4 Mutations A. Kinds of Mutations 1. Gene Mutations 2. Chromosomal Mutations B. Significance of Mutations 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. Interest Grabber continued Section Outline Section 12-5 Section 12-5 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? 12 5 Gene Regulation A. Gene Regulation: An Example B. Eukaryotic Gene Regulation C. Development and Differentiation 3. What type(s) of organic compounds are most likely the ones that help to regulate protein synthesis? Justify your answer. 8
Typical Gene Structure Videos Section 12-5 Regulatory sites Promoter (RNA polymerase binding site) Start transcription strand Stop transcription Click a hyperlink to choose a video. Griffith s Experiment Replication Transcription Protein Synthesis Duplication and Deletion Translocation and Inversion Point Mutations Video 1 Video 2 Griffith s Experiment Replication Video 3 Video 4 Transcription Protein Synthesis 9
Video 5 Video 6 Duplication and Deletion Translocation and Inversion Video 7 Go Online Point Mutations Interactive test Articles on genetics For links on, go to www.scilinks.org and enter the Web Code as follows: cbn-4121. For links on replication, go to www.scilinks.org and enter Web Code as follows: cbn-4122. For links on protein synthesis, go to www.scilinks.org and enter the Web Code as follows: cbn-4123. Interest Grabber Answers Interest Grabber Answers 1. On a sheet of paper, write the word cats. List the letters or units that make up the word cats. The units that make up cats are c, a, t, and s. 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. Student codes may include: Act; Sat; Cat 3. Did any of the codes you formed have the same meaning? No 4. How do you think changing the order of the nucleotides in the codon changes the codon s message? Changing the order of the nucleotides changes the meaning of the codon. 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? Lines will likely look similar. 3. Now, stack the papers, one on top of the other, and hold the papers up to the light. Are the lines the same? Overlaying the papers will show variations in the lines. 4. How could you use the original paper to draw exact copies of the line without tracing it? Possible answer: Cut along the line and use it as a template to draw the line on another sheet of paper. 5. Why is it important that the copies of that are given to new daughter cells be exact copies of the original? Each cell must have the correct, or the cell will not have the correct characteristics. 10
Interest Grabber Answers Interest Grabber Answers 1. Why do you think the library holds some books for reference only? Possible answers: The books are too valuable to risk loss or damage to them. The library wants to make sure the information is always available and not tied up by one person. 2. If you can t borrow a book, how can you take home the information in it? Students may suggest making a photocopy or taking notes. 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? Students will likely say that the cell has some way to copy the information without damaging the. 1. Copy the following information about Protein X: Methionine Phenylalanine Tryptophan Asparagine Isoleucine STOP. 2. Use Figure 12 17 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. Sequences may vary. One example follows: Protein X: mrna: AUG-UUU-UGG-AAU -AUU-UGA; : TAC-AAA-ACC-TTA-TAA-ACT 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. (with deletion of 4th base U) : TAC-AAA-CCT-TAT-AAA-CT 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. mrna: AUG-UUU-GGA-AUA-UUU-GA Codes for amino acid sequence: Methionine Phenylalaine Glycine Isoleucine Phenylalanine? 5. Did this single deletion cause much change in your protein? Explain your answer. Yes, Protein Y was entirely different from Protein X. Interest Grabber Answers 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? Cells do not make all of the proteins for which they have genes (). The structure and function of each cell are determined by the types of proteins present. 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? There must be certain types of compounds that are involved in determining what types of mrna transcripts are made and when this mrna translates at the ribosome. 3. What type(s) of organic compounds are most likely the ones that help to regulate protein synthesis? Justify your answer. The type of compound responsible is probably a protein, specifically enzymes, because these catalyze the chemical reactions that take place. This slide is intentionally blank. 11