interest grabber section outline · interest grabber information, please dna contains the...

1

Go to Section:

Interest Grabber

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.

Section 12-1

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?

Go to Section:

Section Outline

12–1 DNA A. Griffith and Transformation

1. Griffith’s Experiments 2. Transformation

B. Avery and DNA C. The Hershey-Chase Experiment

1. Bacteriophages 2. Radioactive Markers

D. The Components and Structure of DNA 1. Chargaff’s Rules 2. X-Ray Evidence 3. The Double Helix

Section 12-1

Go to Section:

Frederick Griffith (1928)

• Did experiment to figure out how bacteria made people sick, in particular pneumonia. • He isolated two different strains of pneumonia bacteria from mice. • Only one of the strains caused the disease and grew into smooth colonies on culture plates. • The other strain produced colonies that had rough edges. • Griffith injected the mice with the different strains and these were

the results.

Go to Section:

Disease-causing bacteria (smooth

colonies)

Harmless bacteria (rough colonies)

Heat-killed, disease-causing bacteria (smooth colonies)

Control (no growth)



Dies of pneumonia Lives Lives Live, disease-causing bacteria (smooth colonies)

Dies of pneumonia

Section 12-1

Figure 12–2 Griffith’s Experiment

Go to Section:

Disease-causing bacteria (smooth

colonies)



Control (no growth)



Dies of pneumonia Lives Lives Live, disease-causing bacteria (smooth colonies)

Dies of pneumonia

Section 12-1

Figure 12–2 Griffith’s Experiment

Go to Section:

Transformation

• When Griffith mixed the heat-killed bacteria with the harmless bacteria the mice developed pneumonia. • After an examination of the mice’s lungs, Griffith found the disease-causing bacteria. • Somehow, the disease-causing bacteria passed on their disease-causing ability to the harmless strain. • Griffith called this process Transformation, because one strain permanently changed into the other strain.

2

Go to Section:

Oswald Avery (1944)

• Oswald and his crew from the Rockefeller Institute in New York repeated Griffiths experiment. • This time they used enzymes to kill any proteins, lipids, carbohydrates, and RNA. • Transformation still occurred. • Next, they used enzymes that broke down DNA. • Transformation did not occur. • Avery and other scientists discovered that the nucleic acid, DNA, stores and transmits the genetic information from one generation of an organism to the next.

Go to Section:

The Hershey-Chase Experiment

• Alfred Hershey and Martha Chase studied viruses, nonliving particles smaller than a cell that can infect living organisms. • They focused on viruses that infect bacteria. They are known as Bacteriophages. • They are composed of a DNA or RNA core and a protein coat.

Go to Section:

Bacteriophage

1.  The virus attaches to the surface of the cell and injects it genetic information.

2.  The viral genes reproduce many new bateriophages inside the cell.

3.  They gradually destroy the cell. 4.  When the cell bursts open, all the

new viruses are released.

Go to Section:

Bacteriophage with phosphorus-32 in DNA

Phage infects bacterium

Radioactivity inside bacterium

Bacteriophage with sulfur-35 in protein coat


No radioactivity inside bacterium

Figure 12–4 Hershey-Chase Experiment

Section 12-1

Go to Section:







Section 12-1


Go to Section:







Section 12-1


3

Go to Section:

The Components and Structure of DNA

•  DNA = Deoxyribonucleic Acid •  DNA is a long molecule made up of smaller units called nucleotides. •  Nucleotides are made up of three parts:

1.  5-carbon sugar (deoxyribose) 2.  Phosphate group 3.  Nitrogen base

•  Two types of bases: •  Purines (two rings) Pyrimidines (One ring)

1.  Adenine 1. Thymine 2.  Guanine 2. Cytosine

Go to Section:

Purines Pyrimidines

Adenine Guanine Cytosine Thymine

Phosphate group Deoxyribose

Figure 12–5 DNA Nucleotides

Section 12-1

Nitrogen Base

Go to Section:

Chargaff’s Rule

• Chargaff discovered that the percentages of guanine and cytosine bases were almost equal in any sample of DNA. • The same was true for adenine and thymine. • As a result A = T and C = G.

Go to Section:

Percentage of Bases in Four Organisms

Section 12-1

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

Go to Section:

X-Ray Evidence

• In the early 1950’s, Rosalind Franklin used X-ray diffraction to get information about the structure of DNA. • She shot a high power X-ray beam at a concentrated DNA sample. • The results showed an X shaped pattern that shows the DNA strands are twisted around each other like a coil in a spring. This shape is called a helix.

Go to Section:

The Double Helix

• Francis Crick, a British physicist, and James Watson, an American biologist, were trying to understand the structure of DNA. • They tried to build a 3-D model using cardboard and wire, but were unable to get is right. • When they saw the picture from Franklin, Watson got an idea and produced a model that is similar to what we know today. • Watson and Crick’s model of DNA was a double helix, in which two strands were wound around each other.

4

Go to Section:

The Double Helix

• A double helix looks like a twisted ladder or a spiral staircase. • The frame is made up of the 5-carbon sugar and the phosphate group. • The rungs or stairs were made up of the nitrogen bases. • The two strands were held together by special bonds, hydrogen bonds. • The hydrogen bonds could only form between certain bases. • Adenine can only bond to Thymine and Cytosine could only bond to Guanine. • This proved Chargoff’s rule that for every adenine there was one thymine and the same for cytosine and guanine.

Go to Section:

Go to Section:

Hydrogen bonds

Nucleotide

Sugar-phosphate backbone

Key

Adenine (A)

Thymine (T)

Cytosine (C)

Guanine (G)

Figure 12–7 Structure of DNA

Section 12-1

Go to Section:

Interest Grabber

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.

Section 12-2

Go to Section:

Interest Grabber continued

Section 12-2

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?

Go to Section:

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

1. DNA Length 2. Chromosome Structure

B. DNA Replication 1. Duplicating DNA 2. How Replication Occurs

Section 12-2

Section Outline

5

Go to Section:

Chromosome

E. coli bacterium Bases on the chromosome

Prokaryotic Chromosome Structure

Section 12-2

E. coli - Contains 4,639,221 base pairs

Prokaryotes lack nuclei, so their DNA is found in the cytoplasm.

Go to Section:

Chromosome Structure

• Eukaryotic DNA is 1,000 times longer than bacteria. • Eukaryotic chromosomes contain DNA that is tightly wrapped around a protein, called histone, to form a substance called chromatin.

Go to Section:

Figure 12-10 Chromosome Structure of Eukaryotes

Chromosome

Supercoils

Coils

Nucleosome

Histones

DNA

double

helix

Section 12-2

Go to Section:

DNA Replication

• In order for replication to occur, DNA must uncoil from the histones. • Once uncoiled, the DNA polymerase attaches to DNA separating, or unzipping, the two strands. • Free floating nucleotides found in the nucleus will pair up to their complimentary base on the original strand. • Replication will occur in both directions until two new strands are formed.

Go to Section:

Figure 12–11 DNA Replication

Section 12-2

Growth

Growth

Replication fork

DNA polymerase

New strand

Original strand DNA

polymerase

Nitrogenous bases

Replication fork

Original strand

New strand

Go to Section:

Interest Grabber

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.

Section 12-3

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?

6

Go to Section:

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

Section 12-3

Section Outline

Go to Section:

Structure of RNA

RNA (Ribonucleic Acid) differs from DNA in 3 ways: 1. RNA is made up of a single strand of nucleotides 2. RNA contains the sugar Ribose. 3. The nitrogenous base uracil takes the place of

thymine

Go to Section:

Types of RNA

There are three types of RNA

1.  Messenger RNA (mRNA) - Carries information from DNA to the ribosome to build proteins.

2. Ribosomal RNA (rRNA) -Combines with proteins to make up a ribosome

3. Transfer RNA (tRNA) - Transfers a specific amino acid to the ribosome.

Go to Section:

from to to make up

Concept Map

Section 12-3

also called which functions to also called also called which functions to which functions to

can be

RNA

Messenger RNA Ribosomal RNA Transfer RNA

mRNA Carry instructions rRNA Combine

with proteins tRNA Bring

amino acids to ribosome

DNA Ribosome Ribosomes

Go to Section:

RNA DNA

RNA polymerase

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)

Go to Section:

Transcription

• Transcription begins when the DNA separates and RNA Polymerase binds to the promoter on one of the unzipped strands. • Free floating RNA nucleotides will bond to their complimentary bases on the DNA. •  Transcription continues until RNA Polymerase reaches a stop code. • The mRNA releases from the DNA strand, leaves the nucleus, and the DNA goes back to normal.

7

Go to Section:

The Genetic Code

• mRNA contains all the information needed to make proteins. • Every three consecutive bases makes up the code for the amino acids in the protein. • This is called a codon.

Go to Section:

Figure 12–17 The Genetic Code

Section 12-3

Go to Section:

Figure 12–18 Translation

Section 12-3

Go to Section:

Figure 12–18 Translation (continued)

Section 12-3

Go to Section:

Substitution Insertion Deletion

Gene Mutations: Substitution, Insertion, and Deletion

Section 12-4

Go to Section:

Deletion

Duplication

Inversion

Translocation

Figure 12–20 Chromosomal Mutations

Section 12-4

8

Go to Section:

Interest Grabber

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.

Section 12-4

Go to Section:


Section 12-4

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.

Go to Section:

12–4 Mutations A. Kinds of Mutations

1. Gene Mutations 2. Chromosomal Mutations

B. Significance of Mutations

Section 12-4

Section Outline

Go to Section:

Interest Grabber

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.

Section 12-5

Go to Section:


Section 12-5

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.

Go to Section:

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

Section 12-5

Section Outline

9

Go to Section:

Regulatory sites

Promoter (RNA polymerase binding site)

Start transcription

DNA strand

Stop transcription

Typical Gene Structure

Section 12-5

Videos

Click a hyperlink to choose a video. Griffith’s Experiment DNA Replication DNA Transcription Protein Synthesis Duplication and Deletion Translocation and Inversion Point Mutations

Click the image to play the video segment.

Video 1

Griffith’s Experiment


Video 2

DNA Replication


Video 3

DNA Transcription


Video 4

Protein Synthesis

10


Video 5

Duplication and Deletion


Video 6

Translocation and Inversion


Video 7

Point Mutations Interactive test

Articles on genetics

For links on DNA, go to www.SciLinks.org and enter the Web Code as follows: cbn-4121. For links on DNA replication, go to www.SciLinks.org and enter Web Code as follows: cbn-4122. For links on protein synthesis, go to www.SciLinks.org and enter the Web Code as follows: cbn-4123.

Go Online

Interest Grabber Answers

1. On a sheet of paper, write the word cats. List the letters or units that make up the word cats. The units that make up cats are c, a, t, and s.

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. Student codes may include: Act; Sat; Cat

3. Did any of the codes you formed have the same meaning? No

4. How do you think changing the order of the nucleotides in the DNA codon changes the codon’s message? Changing the order of the nucleotides changes the meaning of the codon.


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? Lines will likely look similar.

3. Now, stack the papers, one on top of the other, and hold the papers up to the light. Are the lines the same? Overlaying the papers will show variations in the lines.

4. How could you use the original paper to draw exact copies of the line without tracing it? Possible answer: Cut along the line and use it as a template to draw the line on another sheet of paper.

5. Why is it important that the copies of DNA that are given to new daughter cells be exact copies of the original? Each cell must have the correct DNA, or the cell will not have the correct characteristics.

11


1. Why do you think the library holds some books for reference only? Possible answers: The books are too valuable to risk loss or damage to them. The library wants to make sure the information is always available and not tied up by one person.

2. If you can’t borrow a book, how can you take home the information in it? Students may suggest making a photocopy or taking notes.

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? Students will likely say that the cell has some way to copy the information without damaging the DNA.


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. Sequences may vary. One example follows: Protein X: mRNA: AUG-UUU-UGG-AAU-AUU-UGA; DNA: TAC-AAA-ACC-TTA-TAA-ACT

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. (with deletion of 4th base U) DNA: TAC-AAA-CCT-TAT-AAA-CT

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. mRNA: AUG-UUU-GGA-AUA-UUU-GA Codes for amino acid sequence: Methionine— Phenylalaine—Glycine—Isoleucine—Phenylalanine—?

5. Did this single deletion cause much change in your protein? Explain your answer. Yes, Protein Y was entirely different from Protein X.


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? Cells do not make all of the proteins for which they have genes (DNA). The structure and function of each cell are determined by the types of proteins present.

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? There must be certain types of compounds that are involved in determining what types of mRNA transcripts are made and when this mRNA translates at the ribosome.

3. What type(s) of organic compounds are most likely the ones that help to regulate protein synthesis? Justify your answer. The type of compound responsible is probably a protein, specifically enzymes, because these catalyze the chemical reactions that take place.

This slide is intentionally blank.

interest grabber section outline · interest grabber information, please dna contains the...

Documents