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How to Use This Presentation • To View the presentation as a slideshow with effects select “View” on the menu bar and click on “Slide Show”, or simply press F5 on the top row of your keyboard. • To advance to the next slide click the left mouse button once. • From the Chapter screen you can click on any section to go directly to that section’s presentation. • Blank or “missing” areas of a slide will remain hidden until the left mouse button is clicked. • You may exit the slide show at any time by pressing the Esc key Copyright © by Holt, Rinehart and Winston. All rights reserved. Module C: Chapter 4 Genes and DNA Section 1: What Does DNA Look Like? Section 2: How Does DNA Work? End of Slide Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 1 What Does DNA Look Like? Bellringer Can you explain the difference between traits and characteristics? Which is more closely associated with DNA and genes? Do you know where DNA and genes are found in the body? In specific cells? Write your answers in your science journal. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 1 What Does DNA Look Like? Objectives • List three important events that led to understanding the structure of DNA. • Describe the basic structure of a DNA molecule. • Explain how DNA molecules can be copied. End of Slide Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 1 What Does DNA Look Like? The Pieces of the Puzzle • Nucleotides: The Subunits of DNA DNA is made of subunits called nucleotides that. A nucleotide consists of a sugar, a phosphate, and a base. • Chargaff’s Rule Erwin Chargaff found that the amount of guanine always equals the amount of cytosine. • Franklin’s Discovery Chemist Rosalind Franklin was able to make images of DNA molecules. • Watson and Crick’s Model James Watson and Francis Crick used Chargaff’s and Franklin’s research to build a model of DNA. End of Slide Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 1 What Does DNA Look Like? DNA’s Double Structure • The Double Helix The shape of DNA is shown on the next slide. As you can see, a strand of DNA looks like a twisted ladder. End of Slide Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 1 DNA Structure Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 1 What Does DNA Look Like? Making Copies of DNA • How Copies Are Made During replication, a DNA molecule is split down the middle, where the bases meet. The bases on each side of the molecule are used as a pattern for a new strand. • When Copies Are Made DNA is copied every time a cell divides. End of Slide Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 2 How DNA Works Bellringer Unscramble the following words: tpsoneir neesg Now think of three words you associate with each of the above words and use them all in a paragraph that highlights what you know about DNA. Write your paragraph in your science journal. Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 2 How DNA Works Objectives • Explain the relationship between DNA, genes, and proteins. • Outline the basic steps in making a protein. • Describe three types of mutations, and provide an example of a gene mutation. • Describe two examples of uses of genetic knowledge. End of Slide Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 2 How DNA Works Unraveling DNA • Coiled and Bundled DNA is often wound around proteins, coiled into strands, and then bundled up even more. In a cell that has a nucleus, the strands of DNA and proteins are bundled into chromosomes, as shown on the next slide. End of Slide Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 2 Unraveling DNA Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 2 How DNA Works Genes and Proteins • Proteins and Traits Proteins help determine how tall you grow, what colors you can see, and whether your hair is curly or straight. • Help from RNA Another type of molecule that helps make proteins is called RNA, or ribonucleic acid. RNA is so similar to DNA that RNA can serve as a temporary copy of a DNA sequence. End of Slide Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 2 How DNA Works Genes and Proteins, continued •The Making of a Protein The first step in making a protein is to copy one side of the segment of DNA containing a gene. You can see the next steps of protein production on the following two slides. End of Slide Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 2 The Making of a Protein: A Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 2 The Making of a Protein: B Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 2 How DNA Works Changes in Genes • Mutations Changes in the number, type, or order of bases on a piece of DNA are known as mutations. • Do Mutations Matter? There are three possible consequences to changes in DNA: an improved trait, no change, or a harmful trait. • How Do Mutations Happen? Mutations happen regularly because of random errors when DNA is copied. End of Slide Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 2 How DNA Works An Example of Substitution • Sickle Cell Anemia is a disease that affects red blood cells. It is caused by a substitution that causes a change in a single amino acid in a blood protein. •The DNA sequence GAA, when copied as mRNA, gives the instructions to place the amino acid glutamic acid into the growing protein. •If the original DNA sequence is changed to GTA, the sequence will code for the amino acid valine instead. End of Slide Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 2 How DNA Works An Example of Substitution, continued •When valine is substituted for glutamic acid in a blood protein, the red blood cells are changed into a sickle shape. •The genetic origin of sickle cell anemia is shown on the next slide. End of Slide Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 2 How Sickle Cell Anemia Results from a Mutation Copyright © by Holt, Rinehart and Winston. All rights reserved. Section 2 How DNA Works Uses of Genetic Knowledge • Genetic Engineering Scientists can manipulate individual genes within organisms. This kind of manipulation is called genetic engineering. • Genetic Identification Your DNA is unique, so it can be used like a fingerprint to identify you. DNA fingerprinting identifies the unique patterns in an individual’s DNA. End of Slide Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 6 The Cell in Action Concept Map Use the following terms to complete the concept map on the next slide: mutation, amino acids, nucleotide, DNA, adenine, genes, guanine, proteins, chromosomes, cytosine. Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 6 Concept Map Copyright © by Holt, Rinehart and Winston. All rights reserved. Chapter 6 Concept Map Copyright © by Holt, Rinehart and Winston. All rights reserved.