Download A. DNA and Chromosomes

Chapter 12
DNA and RNA
Lecture
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?
Section 12-1 DNA
Objective:
• Summarize the relationship between genes and DNA
• Describe the overall structure of the DNA molecule
Homework section 12-1
Write out all key concepts.
Define each vocabulary word in at least 1 complete
sentence.
12–1 DNA
A.
Griffith and Transformation
B.
Avery and DNA
C.
The Hershey-Chase Experiment
D.
The Structure of DNA
A.
Griffith and Transformation
– 1928 Frederick Griffith, British scientist
2.
Transformation
Figure 12–2 Griffith’s Experiment
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
Lives
Lives
Control
(no growth)
Harmless bacteria
(rough colonies)
Dies of pneumonia
Live, disease-causing
bacteria (smooth colonies)
Figure 12–2 Griffith’s Experiment
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
Lives
Lives
Control
(no growth)
Harmless bacteria
(rough colonies)
Dies of pneumonia
Live, disease-causing
bacteria (smooth colonies)
B.
Avery and DNA
C.
The Hershey-Chase Experiment
1.Bacteriophages
2.Radioactive Markers
Figure 12–4 Hershey-Chase
Experiment
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
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
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
D. The Structure of DNA
1. Chargaff’s Rules
Figure 12–5 DNA Nucleotides
Purines
Adenine
Guanine
Phosphate
group
Pyrimidines
Cytosine
Thymine
Deoxyribose
2. X-Ray Evidence
Percentage of Bases in Four
Organisms
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
3. The Double Helix
Figure 12–7 Structure of DNA
Nucleotide
Hydrogen
bonds
Sugar-phosphate
backbone
Key
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
Homework section 12-1
Answer all 5 questions on page 294 in at least 3 complete
sentences.
Section 12-2 Chromosome and DNA Replication
Objective:
• Summarize the events of DNA replication
• Relate the DNA molecule to chromosome structure
Homework section 12-2
• Write out all key concepts.
• Define each vocabulary word in at least one complete
sentence.
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.
1. On a sheet of paper, draw a curving or zig-zagging line that divides the
paperSection
into 12-2
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?
12–2 Chromosomes and DNA Replication
A. DNA and Chromosomes
B.
DNA Replication
A.
DNA and Chromosomes
Prokaryotic Chromosome Structure
Chromosome
E. coli bacterium
Bases on the chromosome
B. DNA Replication
A. DNA and Chromosomes
1. DNA Length
2.
Chromosome Structure
Figure 12-10 Chromosome
Structure of Eukaryotes
Chromosome
Nucleosome
DNA
double
helix
Coils
Supercoils
Histones
B. DNA Replication
1. Duplicating DNA
2. How Replication Occurs
Figure 12–11 DNA Replication
New strand
Original
strand
DNA
polymerase
Growth
DNA
polymerase
Growth
Replication
fork
Replication
fork
New strand
Original
strand
Nitrogenous
bases
Homework section 12-2
Answer all questions 299 in at least 3 complete sentences.
Go to
Section:
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 12-3 RNA and Protein Synthesis
Objective:
• How does RNA differ from DNA
• Name three main types of RNA
• Describe transcription and the editing of RNA
• Identify the genetic code
• Summarize translation
• Explain the relationship between genes and proteins
Go to
Section:
Homework 12-3 RNA and Protein Synthesis
Write out all key concepts.
Define all vocabulary words in at least one complete
sentence.
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
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
C. Transcription
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
D. RNA Editing
Figure 12–17 The Genetic Code
E. The Genetic Code
F. Translation
Figure 12–18 Translation
Nucleus
Messenger RNA
Messenger RNA is transcribed in the nucleus.
Phenylalanine
tRNA
mRNA
Transfer RNA
Methionine
The mRNA then enters the cytoplasm and
attaches to a ribosome. Translation begins at
AUG, the start codon. Each transfer RNA has
an anticodon whose bases are complementary
to a codon on the mRNA strand. The ribosome
positions the start codon to attract its
anticodon, which is part of the tRNA that binds
methionine. The ribosome also binds the next
codon and its anticodon.
Ribosome
mRNA
Lysine
Start codon
Figure 12–18 Translation
(continued)
The Polypeptide “Assembly Line”
The ribosome joins the two amino acids—
methionine and phenylalanine—and breaks
the bond between methionine and its tRNA.
The tRNA floats away, allowing the ribosome
to bind to another tRNA. The ribosome moves
along the mRNA, binding new tRNA molecules
and amino acids.
Lysine
Growing polypeptide chain
Ribosome
tRNA
tRNA
mRNA
Completing the Polypeptide
mRNA
Ribosome
Translation direction
The process continues until the ribosome reaches
one of the three stop codons. The result is a
growing polypeptide chain.
G. The Roles of RNA and DNA
H. Genes and Proteins
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.
1. Copy the following information about Protein X: Methionine—
Phenylalanine—Tryptophan—Asparagine—Isoleucine—STOP.
Section 12-4
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.
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
Transfer RNA
also called
which functions to
tRNA
Bring
amino acids to
ribosome
12–4 Mutations
Objective:
•
Contrast gene mutations and chromosomal mutations.
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?
12–4 Homework
Write out all key concepts.
Define each vocabulary word in at least one complete sentence.
12–4 Mutations
A. Gene Mutations
B. Chromosomal Mutations
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.
Gene Mutations:
Substitution, Insertion, and Deletion
Section 12-4
Deletion
Substitution
Insertion
Figure 12–20 Chromosomal Mutations
Deletion
Duplication
Inversion
Translocation
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.
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.
12–5 Gene Regulation
A. Gene Regulation: An Example
B. Eukaryotic Gene Regulation
C. Regulation and Development
Typical Gene Structure
Regulatory
sites
Promoter
(RNA polymerase
binding site)
Start transcription
DNA strand
Stop transcription