Chapter 12 DNA and RNA Lecture

Order! Order! Genes are made of DNA, a large, complex molecule. DNA 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 DNA codon changes the codon’s message?

Section 12-1 DNA Objective: Summarize the relationship between genes and DNA Describe the overall structure of the DNA molecule

Homework section 12-1 Write out all key concepts. Define each vocabulary word in at least 1 complete sentence.

12–1 DNA A. Griffith and Transformation B. Avery and DNA C. The Hershey-Chase Experiment D. The Structure of DNA

A. Griffith and Transformation 1928 Frederick Griffith, British scientist

2. Transformation

Figure 12–2 Griffith’s Experiment Heat-killed, disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Control (no growth) Harmless bacteria (rough colonies) Heat-killed, disease-causing bacteria (smooth colonies) Disease-causing bacteria (smooth colonies) Dies of pneumonia Dies of pneumonia Lives Lives Live, disease-causing bacteria (smooth colonies)

Figure 12–2 Griffith’s Experiment Heat-killed, disease-causing bacteria (smooth colonies) Harmless bacteria (rough colonies) Control (no growth) Harmless bacteria (rough colonies) Heat-killed, disease-causing bacteria (smooth colonies) Disease-causing bacteria (smooth colonies) Dies of pneumonia Dies of pneumonia Lives Lives Live, disease-causing bacteria (smooth colonies)

B. Avery and DNA

C. The Hershey-Chase Experiment 1. Bacteriophages 2. Radioactive Markers

Figure 12–4 Hershey-Chase Experiment Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium

Figure 12–4 Hershey-Chase Experiment Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium

Figure 12–4 Hershey-Chase Experiment Bacteriophage with phosphorus-32 in DNA Phage infects bacterium Radioactivity inside bacterium Bacteriophage with sulfur-35 in protein coat Phage infects bacterium No radioactivity inside bacterium

D. The Structure of DNA 1. Chargaff’s Rules

Figure 12–5 DNA Nucleotides Purines Pyrimidines Adenine Guanine Cytosine Thymine Phosphate group Deoxyribose

2. X-Ray Evidence

Percentage of Bases in Four Organisms Source of DNA A T G C Streptococcus 29.8 31.6 20.5 18.0 Yeast 31.3 32.9 18.7 17.1 Herring 27.8 27.5 22.2 22.6 Human 30.9 29.4 19.9 19.8

3. The Double Helix

Figure 12–7 Structure of DNA Nucleotide Hydrogen bonds Sugar-phosphate backbone Key Adenine (A) Thymine (T) Cytosine (C) Guanine (G)

Homework section 12-1 Answer all 5 questions on page 294 in at least 3 complete sentences.

Section 12-2 Chromosome and DNA Replication Objective: Summarize the events of DNA replication Relate the DNA molecule to chromosome structure

Homework section 12-2 Write out all key concepts. Define each vocabulary word in at least one complete sentence.

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 DNA code. Before a cell can divide, the DNA must be copied so that there are two sets ready to be distributed to the new cells.

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 DNA that are given to new daughter cells be exact copies of the original? Section 12-2

12–2 Chromosomes and DNA Replication A. DNA and Chromosomes B. DNA Replication

A. DNA and Chromosomes

Prokaryotic Chromosome Structure E. coli bacterium Bases on the chromosome

B. DNA Replication

A. DNA and Chromosomes 1. DNA Length 2. Chromosome Structure

Figure 12-10 Chromosome Structure of Eukaryotes Nucleosome Chromosome DNA double helix Coils Supercoils Histones

B. DNA Replication 1. Duplicating DNA

2. How Replication Occurs

Figure 12–11 DNA Replication Original strand DNA polymerase New strand Growth DNA polymerase Growth Replication fork Replication fork Nitrogenous bases New strand Original strand

Answer all questions 299 in at least 3 complete sentences. Homework section 12-2 Answer all questions 299 in at least 3 complete sentences. Go to Section:

1. Why do you think the library holds some books for reference only? Information, Please DNA contains the information that a cell needs to carry out all of its functions. In a way, DNA 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 DNA, yet DNA does not leave the nucleus. How do you think the information in DNA might get from the nucleus to the rest of the cell? Go to Section:

Section 12-3 RNA and Protein Synthesis Objective: How does RNA differ from DNA Name three main types of RNA Describe transcription and the editing of RNA Identify the genetic code Summarize translation Explain the relationship between genes and proteins Go to Section:

Homework 12-3 RNA and Protein Synthesis Write out all key concepts. Define all vocabulary words in at least one complete sentence.

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 DNA H. Genes and Proteins

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 DNA H. Genes and Proteins

C. Transcription

Figure 12–14 Transcription Section 12-3 Adenine (DNA and RNA) Cystosine (DNA and RNA) Guanine(DNA and RNA) Thymine (DNA only) Uracil (RNA only) RNA polymerase DNA RNA

D. RNA Editing

Figure 12–17 The Genetic Code

E. The Genetic Code

F. Translation

Figure 12–18 Translation mRNA Nucleus Messenger RNA mRNA Lysine Messenger RNA is transcribed in the nucleus. mRNA Lysine Phenylalanine tRNA 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. Methionine Ribosome mRNA Start codon

Figure 12–18 Translation (continued) 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. Growing polypeptide chain Ribosome tRNA Lysine tRNA mRNA Completing the Polypeptide The process continues until the ribosome reaches one of the three stop codons. The result is a growing polypeptide chain. mRNA Translation direction Ribosome

G. The Roles of RNA and DNA

H. Genes and Proteins

Determining the Sequence of a Gene DNA 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—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 DNA 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 DNA 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

Bring amino acids to ribosome Concept Map Section 12-3 RNA 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 DNA Ribosome Ribosomes

12–4 Mutations Objective: Contrast gene mutations and chromosomal mutations.

Information, Please DNA contains the information that a cell needs to carry out all of its functions. In a way, DNA 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. Why do you think the library holds some books for reference only? 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 DNA, yet DNA does not leave the nucleus. How do you think the information in DNA might get from the nucleus to the rest of the cell?

12–4 Homework Write out all key concepts. Define each vocabulary word in at least one complete sentence.

12–4 Mutations A. Gene Mutations B. Chromosomal Mutations

Determining the Sequence of a Gene DNA contains the code of instructions for cells. Sometimes, an error occurs when the code is copied. Such errors are called mutations.

Gene Mutations: Substitution, Insertion, and Deletion Section 12-4 Deletion Substitution Insertion

Figure 12–20 Chromosomal Mutations Deletion Duplication Inversion Translocation

Regulation of Protein Synthesis Every cell in your body, with the exception of gametes, or sex cells, contains a complete copy of your DNA. 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 DNA (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.

12–5 Gene Regulation Gene Regulation: An Example Eukaryotic Gene Regulation C. Regulation and Development

Typical Gene Structure Promoter (RNA polymerase binding site) Regulatory sites DNA strand Start transcription Stop transcription