Unraveling the Mystery of DNA: Structure, Genes, and Replication

1. Chapter 6 Section 1 What Does DNA Look Like? Bellringer • Give an example of the difference between traits and characteristics. • Sample answer: Eye color is a characteristic, while having blue eyes is a trait. • Where are genes found in cells? • in chromosomes; in cells that have nuclei, chromosomes are within the nucleus • Write your answers in your science notebook.

2. Genes and DNA Chapter 6 Table of Contents Section 1 What Does DNA Look Like? Section 2 How DNA Work

3. Chapter 6 Section1 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.

4. Chapter 6 Section1 What Does DNA Look Like?

5. Section1 The Diversity of Cells (REVIEW!!!) Chapter 3 • Genetic MaterialAll cells contain DNA at some • point in their life. DNA is genetic material that • carries information needed to make new cells and • new organisms. • Chromosomes • are made of • protein and • DNA.

6. Chapter 6 Section1 What Does DNA Look Like? The Pieces of the Puzzle • DNAstands for deoxyribonucleic acid. DNA is the genetic material that determines inherited characteristics. • Nucleotides: The Subunits of DNA DNA is made of subunits called nucleotides. A nucleotide consists of a sugar, a phosphate, and a base.

7. Chapter 6 Section1 What Does DNA Look Like? The Pieces of the Puzzle, continued • Chargaff’s Rule Erwin Chargaff found that the amount of adenine in DNA always equals the amount of thymine, and the amount of guanine always equals the amount of cytosine. • CHARGAFF’S RULE: • C = G and A = T

8. Chapter 6 Section1 What Does DNA Look Like? The Pieces of the Puzzle • Franklin’s Discovery Chemist Rosalind Franklin was able to make images of DNA molecules by using X-ray diffraction.

9. Chapter 6 Section1 What Does DNA Look Like? The Pieces of the Puzzle, continued • Watson and Crick’s Model James Watson and Francis Crick used Chargaff’s and Franklin’s research to build a model of DNA. • The model, which looked like a long, twisted ladder, eventually helped explain how DNA is copied and how it functions in the cell.

10. Chapter 6 Section1 What Does DNA Look Like? DNA’s Double Structure • The Double Helix The • shape of DNA is known • as a double helix. • The two sides of the • ladder are made of • alternating sugar parts • and phosphate parts. • The rungs of the ladder • are made of a pair of bases.

11. Chapter 6 Section1 What Does DNA Look Like? 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.

12. Section1 What Does DNA Look Like? Chapter 6 Making Copies of DNA • When Copies Are Made DNA is copied every time a cell divides. Each new cell gets a complete copy of all the DNA.

13. Section1 What Does DNA Look Like? Chapter 6 DNA Replication Click below to watch the Visual Concept. You may stop the video at any time by pressing the Esc key. Visual Concept

14. Section2 How DNA Works Chapter 6 Bellringer • Unscramble the following words and use them in one sentence: • tpsoneir • neesg • (HINT: We discussed these words in Chapters 2 & 5) • Write your paragraph in your science notebook.

15. Section2 How DNA Works Chapter 6 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.

17. Section2 How DNA Works Chapter 6 Unraveling DNA • 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.

18. Chapter 6 Section2 How DNA Works

19. Section2 How DNA Works Chapter 6 Unraveling DNA • A geneconsists of a string of nucleotides that give the cell information about how to make a specific trait.

20. Section2 How DNA Works Chapter 6 • Reading Check: • What makes • up a gene? • A string of nucleotides that give the cell information about how to make a specific trait.

21. Section2 How DNA Works Chapter 6 • Genes and Proteins • Three bases code • for specific amino • acids. • Proteins and Traits Proteins act as chemical triggers for many of the processes within cells. Proteins help determine traits.

22. Section2 How DNA Works Chapter 6 • 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.

23. Section2 How DNA Works Chapter 6 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. This copy is called messenger RNA (mRNA). • mRNA is ribonucleic acid that copies DNA and goes to the ribosome.

24. Section2 How DNA Works Chapter 6 Genes and Proteins • A ribosomeis a cell • organelle where protein • is synthesized and is • composed of RNA and • protein. A ribosome uses mRNA, transfer RNA • (tRNA), and amino acids to make proteins. • tRNA is a type of RNA that delivers amino acids to • make a protein. • You can see the steps of protein production on the • following two slides.

25. Section2 How DNA Works Chapter 6

26. Section2 How DNA Works Chapter 6

27. Section2 How DNA Works Chapter 6 • Reading Check:What do the transfer RNA molecules transfer? • They transfer amino acids to the ribosome.

28. Section2 How DNA Works Chapter 6 Changes in Genes • Mutations Changes in the number, type, or order of bases on a piece of DNA are known as mutations. There are 3 types of mutations: • deletion • insertion • substitution.

29. Section2 How DNA Works Chapter 6 Changes in Genes, continued • 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. Any physical or chemical agent that can cause a mutation in DNA is called a mutagen. • Asbestos • * The great discovery!  • * Not so great discovery. 

30. Section2 How DNA Works Chapter 6 Carcinogens and Mutagens Click below to watch the Visual Concept. You may stop the video at any time by pressing the Esc key. Visual Concept

31. Section2 How DNA Works Chapter 6 • Reading Check: • What is a • mutagen? • A mutagen is a physical or chemical agent that can cause a mutation in DNA.

32. Section2 How DNA Works Chapter 6 An Example of Substitution • A mutation, such as a substitution, can be harmful because it may cause a gene to produce the wrong protein. • A simple change in an amino acid can cause a disease such as sickle cell anemia, as shown on the next slide.

34. Chapter 6 Section2 How DNA Works Uses of Genetic Knowledge • Genetic Engineering Scientists can manipulate individual genes within organisms. This kind of manipulation is called genetic engineering.

35. Chapter 6 Section2 How DNA Works Uses of Genetic Knowledge • 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.

36. Section2 How DNA Works Chapter 6 • Reading Check:What is a clone? • A clone is a near-identical copy of another • organism with the original organism’s genes.

37. Chapter 6 Genes and DNA • Quick Check Quiz! 1. What is the function of the ribosome? • In the ribosome, the DNA code is translated • into proteins!!! • 2. What are some causes of DNA mutations? • UV radiation, cigarette smoke, X-rays, etc.

38. Chapter 6 Genes and DNA Section 6.2 Summary • A gene is a set of instructions for assembling a • protein. DNA is the molecular carrier of these genetic • instructions. • Every organism has DNA in its cells. Humans have • about 2 m of DNA in each cell. • Within a gene, each group of three bases codes for • one amino acid. A sequence of amino acids is linked • to make a protein. • Proteins are fundamental to the function of cells and • the expression of traits. (continued on next slide)

39. Chapter 6 Genes and DNA Section 6.2 Summary • Proteins are assembled within the cytoplasm through • a multi-step process that is assisted by several forms • of RNA. • Genes can become mutated when the order of the • bases is changed. Three main types of mutations are • possible: insertion, deletion, and substitution. • Genetic knowledge has many practical uses. Some • applications of genetic knowledge are controversial.

40. Chapter 6 Genes and DNA Concept Map Use the terms below to complete the concept map on the next slide.

41. Concept Map Chapter 6

42. Chapter 6 Concept Map

43. End of Chapter 6 Show

44. Standardized Test Preparation Chapter 6 Reading Read each of the passages. Then, answer the questions that follow each passage.

45. VOCABULARY TERMS Chapter 6 amino acids chemical parts that are transferred to the ribosome by transfer RNA and matched to messenger RNA

46. VOCABULARY TERMS Chapter 6 chromosomes in a cell nucleus, the structures that strands of DNA are bundled into

47. VOCABULARY TERMS Chapter 6 DNA material shaped like a double helix that determines inherited characteristics

48. VOCABULARY TERMS Chapter 6 gene a string of nucleotides that give the cell information about how to make a specific trait

49. VOCABULARY TERMS Chapter 6 guanine the base complementary to cytosine

50. VOCABULARY TERMS Chapter 6 mutagen a physical or chemical agent that can cause a mutation