Mr. Carpenter s Biology DNA and RNA 9/10. Name Pd

Transcription

1 Mr. Carpenter s Biology DNA and RNA 9/10 Name Pd 1

2 Chapter 9 Vocabulary Vaccine Virulent Transformation Bacteriophage Nucleotide Deoxyribose DNA Replication DNA Helicase Replication fork DNA Polymerase 2

3 Name: Class: Date: Chapter 9 DNA: The Genetic Material Section 1: Identifying the Genetic Material I. Transformation: Griffith s Experiments In 1928,, a bacteriologist, was trying to prepare a against pneumonia. A is a substance that is prepared from killed or weakened disease-causing agents, including certain bacteria. The vaccine is introduced into the body to the body against future by the disease-causing agent. Griffith s Experiments Griffith discovered that bacteria could turn virulent when mixed with bacteria that cause disease. A bacteria that is is able to cause disease. Griffith had discovered what is now called, a change in genotype caused when cells take up foreign genetic material. II. Transformation continued Avery s Experiments In 1944, a series of experiments showed: *The activity of the material responsible for transformation is not affected by - enzymes. *HOWEVER, the activity IS stopped by a - enzyme. 3

4 Thus, almost 100 years after Mendel s experiments, and his co-workers demonstrated that is the material responsible for transformation. III. Viral Genes and DNA DNA s Role Revealed In 1952, Alfred Hershey and Martha Chase used the T2 to prove that DNA carried material. A, also referred to as phage, is a that infects bacteria. When infect bacterial cells, the phages are able to produce more viruses, which are released when the bacterial cells. DNA s Role Revealed Hershey and Chase carried out the following experiment: Step 1: T2 phages were labeled with isotopes. Step 2: The phages E. coli bacterial cells. Step 3: Bacterial cells were spun to remove the virus's coats. DNA s Role Revealed Hershey and Chase concluded that the of viruses is injected into the bacterial cells, while most of the viral remain outside. The injected DNA molecules causes the bacterial cells to produce more and proteins. This meant that the, rather than, is the hereditary material, at least in viruses. 4

5 Section 2: The Structure of DNA I. A Winding Staircase and determined that a DNA molecule is a two strands twisted around each other, like a winding staircase. are the subunits that make up DNA. Each nucleotide is made of three parts: The five-carbon sugar in DNA nucleotides is called. The nitrogen base in a nucleotide can be either a bulky, double-ring, or a smaller, single-ring. 5

6 I. Discovering DNA s Structure A. Chargaff s Observations In 1949, Erwin Chargaff observed that for each organism he studied, the amount of always equaled the amount of ( = ). Likewise, the amount of always equaled the amount of ( = ). However, the amount of adenine + thymine and of guanine + cytosine between different organisms. B. Wilkins and Franklin s Photographs By analyzing the complex patterns on photo, scientists can determine the structure of the molecule. In 1952, Maurice Wilkins and Rosalind Franklin (pictured at the left) developed high-quality diffraction photographs of strands of. These photographs (seen at left) suggested that the DNA molecule resembled a tightly coiled and was composed of two or three chains of. C. Watson and Crick s DNA Model Franklin s image was such a for them that it only took them a few weeks to figure out the structure of DNA after they saw it. In 1953, Watson and Crick (pictured to the right) built a model of DNA with the configuration of a double helix, a 6

7 of two strands of nucleotides twisting around a central axis. The double-helical model of DNA takes into account observations and the on Franklin s X-ray diffraction photographs. In 1962 Watson, Crick, and Wilson received the. Rosalind Franklin did not share in the award because she died in D. Pairing Between Bases An on one strand always pairs with a on the opposite strand, and a on one strand always pairs with a on the opposite strand. These are supported by Chargaff s observations. The strictness of base-pairing results in two strands that contain. The diagram of DNA below the helix makes it easier to visualize the base-pairing that occurs between DNA strands. 7

8 Section 3: The Replication of DNA I. Roles of Enzymes in DNA Replication The complementary structure of is used as a basis to make exact copies of the DNA each time a cell. The process of making a copy of DNA is called. DNA replication occurs during the (S) phase of the cell cycle, before a cell divides. DNA replication occurs in three steps: Step 1: open the double helix by breaking the bonds that link the complementary nitrogen bases between the two strands. The areas where the double separates are called. Step 2: At the replication fork, enzymes known as move along each of the DNA strands. DNA polymerases add to the exposed nitrogen bases, according to the rules. Step 3: Two molecules form that are to the original DNA molecule. 8

9 II. Checking for Errors In the course of DNA replication, sometimes occur and the wrong is added to the new strand. An important feature of DNA is that DNA polymerases have a role. This reduces errors in DNA replication to about error per 1 billion nucleotides. III. The Rate of Replication does NOT begin at one end of the DNA and end at the other. The DNA molecules found in usually have two replication forks that begin at a single point. The replication move away from each other until they meet on the opposite side of the DNA. In cells, each chromosome contains a single, long strand of DNA. Each chromosome is replicated in about 100 sections that are 100,000 long, EACH section has starting point. With multiple replication forks working in concert, an entire human chromosome can be replicated in. Replication Forks Increase the Speed of Replication 9

10 Chapter 9 Section 1 Questions 1. What question did Mendel s experiments answer? 2. What question did Mendel s experiment create? 3. What was Frederick Griffith trying to find in his experiments? 4. How does a vaccine work? 5. How were the two types of bacteria different in Griffith s experiments? Strain #1- Strain #2-6. What happened when Griffith injected the mice with S bacteria? 7. What happened when Griffith injected the mice with R bacteria? 8. What happened when Griffith injected the mice with heated-killed S bacteria? 9. What happened when Griffith injected the mice with heated-killed S bacteria and live R bacteria? 10. How did Griffith explain what happened in his experiment? 11. What did Oswald Avery discover? 12. What did Hershey and chase conclude from their experiments? 10

11 Chapter 9 Section 2 Questions 1. What was the importance of discovering DNA s structure? 2. What is meant by double helix? 3. Who discovered the structure of the DNA molecule? 4. What are the three parts of the nucleotide? a.. b.. c.. 5. What is the five carbon sugar in DNA called? 6. What parts of the DNA nucleotide remains the same? 7. What part changes in DNA nucleotide? 8. What are the four different nitrogen bases in DNA? a.. b.. c.. d.. 11

12 9. What type of bond holds the two strands of the double helix together? 10. How did Erwin Chargaff contribute to Watson and Crick s discovery? 11. How did Maurice Wilkins and Rosalind contribute to Watson and Crick s discovery? 12. What does adenine always pair with? 13. What does guanine always pair with? 14. What does cytosine always pair with? 15. What does thymine always pair with? Chapter 9 Section 3 Questions 1. When does DNA replication occur during the cell cycle? 2. What enzyme opens the DNA s double helix by breaking the hydrogen bonds? 3. What is the area where the double helix is held apart called? 4. What enzyme adds the new nucleotides to the original DNA strand? 5. What enzyme is responsible for proof-reading the new DNA strands? 6. How many replication forks does prokaryotic DNA have? 7. How many replication forks does eukaryotic DNA have? 12