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Interest Grabber
Section 12-1
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.
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
Section 12-1
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
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:
Figure 12–2 Griffith’s Experiment
Section 12-1
Heat-killed,
disease-causing
bacteria (smooth
colonies)
Disease-causing
bacteria (smooth
colonies)
Harmless bacteria Heat-killed, disease(rough colonies) causing bacteria
(smooth colonies)
Dies of pneumonia
Go to
Section:
Lives
Lives
Control
(no growth)
Harmless bacteria
(rough colonies)
Dies of pneumonia
Live, disease-causing
bacteria (smooth colonies)
Figure 12–2 Griffith’s Experiment
Section 12-1
Heat-killed,
disease-causing
bacteria (smooth
colonies)
Disease-causing
bacteria (smooth
colonies)
Harmless bacteria Heat-killed, disease(rough colonies) causing bacteria
(smooth colonies)
Dies of pneumonia
Go to
Section:
Lives
Lives
Control
(no growth)
Harmless bacteria
(rough colonies)
Dies of pneumonia
Live, disease-causing
bacteria (smooth colonies)
Figure 12–4 Hershey-Chase Experiment
Section 12-1
Go to
Section:
Bacteriophage with
phosphorus-32 in
DNA
Phage infects
bacterium
Radioactivity inside
bacterium
Bacteriophage with
sulfur-35 in protein
coat
Phage infects
bacterium
No radioactivity inside
bacterium
Figure 12–4 Hershey-Chase Experiment
Section 12-1
Go to
Section:
Bacteriophage with
phosphorus-32 in
DNA
Phage infects
bacterium
Radioactivity inside
bacterium
Bacteriophage with
sulfur-35 in protein
coat
Phage infects
bacterium
No radioactivity inside
bacterium
Figure 12–4 Hershey-Chase Experiment
Section 12-1
Go to
Section:
Bacteriophage with
phosphorus-32 in
DNA
Phage infects
bacterium
Radioactivity inside
bacterium
Bacteriophage with
sulfur-35 in protein
coat
Phage infects
bacterium
No radioactivity inside
bacterium
Figure 12–5 DNA Nucleotides
Section 12-1
Purines
Adenine
Guanine
Phosphate
group
Go to
Section:
Pyrimidines
Cytosine
Thymine
Deoxyribose
Figure 12–7 Structure of DNA
Section 12-1
Nucleotide
Hydrogen
bonds
Sugar-phosphate
backbone
Key
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
Go to
Section:
Interest Grabber
Section 12-2
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.
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:
Section Outline
Section 12-2
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
Go to
Section:
Prokaryotic Chromosome Structure
Section 12-2
Chromosome
E. coli bacterium
Bases on the chromosome
Go to
Section:
Figure 12-10 Chromosome Structure
of Eukaryotes
Section 12-2
Chromosome
Nucleosome
DNA
double
helix
Coils
Supercoils
Histones
Go to
Section:
Figure 12–11 DNA Replication
Section 12-2
New strand
Original
strand
DNA
polymerase
Growth
DNA
polymerase
Growth
Replication
fork
Replication
fork
New strand
Go to
Section:
Original
strand
Nitrogenous
bases
Interest Grabber
Section 12-3
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.
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?
Go to
Section:
Section Outline
Section 12-3
12–3
RNA and Protein Synthesis
A.
B.
C.
D.
E.
F.
G.
H.
Go to
Section:
The Structure of RNA
Types of RNA
Transcription
RNA Editing
The Genetic Code
Translation
The Roles of RNA and DNA
Genes and Proteins
Concept Map
Section 12-3
RNA
can be
Messenger RNA
also called
Ribosomal RNA
which functions to
mRNA
Carry instructions
also called
which functions to
rRNA
Combine
with proteins
from
to
to make up
DNA
Ribosome
Ribosomes
Go to
Section:
Transfer RNA
also called
which functions to
tRNA
Bring
amino acids to
ribosome
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)
RNA
polymerase
DNA
RNA
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:
Interest Grabber
Section 12-4
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.
Go to
Section:
Interest Grabber continued
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:
Section Outline
Section 12-4
12–4
Mutations
A. Kinds of Mutations
1. Gene Mutations
2. Chromosomal Mutations
B. Significance of Mutations
Go to
Section:
Gene Mutations: Substitution, Insertion,
and Deletion
Section 12-4
Deletion
Substitution
Go to
Section:
Insertion
Figure 12–20 Chromosomal Mutations
Section 12-4
Deletion
Duplication
Inversion
Translocation
Go to
Section:
Interest Grabber
Section 12-5
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.
Go to
Section:
Interest Grabber continued
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:
Section Outline
Section 12-5
12–5
Gene Regulation
A. Gene Regulation: An Example
B. Eukaryotic Gene Regulation
C. Development and Differentiation
Go to
Section:
Typical Gene Structure
Section 12-5
Regulatory
sites
Promoter
(RNA polymerase
binding site)
Start transcription
Go to
Section:
DNA strand
Stop transcription
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
Go Online
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.
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.
Interest Grabber Answers
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.
Interest Grabber Answers
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-AAUAUU-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.
Interest Grabber Answers
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.