1

Mr. Carpenter’s Biology DNA and RNA 9/10

Name ________________ Pd ____

2

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

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.

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.

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:

1. 2. 3.

•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 ______________________.

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

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 1958. 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.

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.

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

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?

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. .

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?