Section Outline

1
Section Outline
Section 12-1

• 121 DNA and RNA
• DNA is like the architects master plan for a
  building. This valuable plan and the model never
  leave his office.
• RNA is like the actual blueprints taken to the
  jobsite where the actual construction occurs.
• A. DNA was discovered when transformation was
  observed in 2 strains of bacteria
• 1. Griffiths Experiments p. 288
• 2. Transformation process in which one strain
  of bacteria is changed by a gene or genes from
  another strain of bacteria.

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2
Figure 122 Griffiths Experiment
Section 12-1
Heat-killed, disease-causing bacteria (smooth
colonies)
Harmless bacteria (rough colonies)
Control(no growth)
Harmless bacteria (rough colonies)
Heat-killed, disease-causing bacteria (smooth
colonies)
Disease-causing bacteria (smooth colonies)
Dies of pneumonia
Dies of pneumonia
Lives
Lives
Live, disease-causingbacteria (smooth colonies)
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3
Figure 122 Griffiths Experiment
Section 12-1
Heat-killed, disease-causing bacteria (smooth
colonies)
Harmless bacteria (rough colonies)
Control(no growth)
Harmless bacteria (rough colonies)
Heat-killed, disease-causing bacteria (smooth
colonies)
Disease-causing bacteria (smooth colonies)
Dies of pneumonia
Dies of pneumonia
Lives
Lives
Live, disease-causingbacteria (smooth colonies)
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4
Transformation

• Griffiths 1928 experiment showed that some
  factor was responsible for transferring the
  disease causing ability of the virulent strain to
  the harmless strain. What do you think is the
  name of this factor?

5
Discovery of DNA as the Factor

• Avery and DNA
• In 1944, Oswald Avery and others used
  enzymes to destroy lipids, carbohydrates,
  proteins, and RNA in an extract from the disease
  causing bacteria. Transformation still occurred,
  so obviously the molecules they had destroyed
  were not responsible for transformation.
• Next, they repeated the experiment, this
  time using enzymes that would destroy DNA as
  well. Transformation no longer occurred, showing
  them that the factor responsible for
  transformation was DNA.

6
3 Important Gene Functions

• Carry information from one generation to the next
• Put that information to work by determining the
  heritable characteristics of organisms
• 3. Have to be easily copied each time a cell
  divides

7
C. The Structure of DNA

• Made of monomers called nucleotides, each
  containing 3 basic parts
• 5 carbon sugar called deoxyribose
• Phosphate group
• Nitrogenous (nitrogen-containing) base
• 1. adenine
• 2. guanine
• 3. cytosine
• 4. thymine
• Chargaffs Rules there exists a 11 ratio of
  the base pairs
• AdenineThymine
  CytosineGuanine
• Why does this ratio exist? We now know why, but
  not until the
• double helix structure was determined by Watson
  and Crick in 1953.

8
Figure 125 DNA Nucleotides
Section 12-1
Purines
Pyrimidines
Adenine
Guanine
Cytosine
Thymine
Phosphate group
Deoxyribose
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9
Figure 127 Structure of DNA
Section 12-1
Nucleotide
Hydrogen bonds
Sugar-phosphate backbone
Key Adenine (A) Thymine (T) Cytosine (C) Guanine
(G)
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10
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 2
9.4 19.9 19.8
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11
Figure 124 Hershey-Chase Experiment
Section 12-1
Bacteriophage with phosphorus-32 in DNA
Phage infectsbacterium
Radioactivity inside bacterium
Bacteriophage with sulfur-35 in protein coat
Phage infectsbacterium
No radioactivity inside bacterium
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12
Figure 124 Hershey-Chase Experiment
Section 12-1
Bacteriophage with phosphorus-32 in DNA
Phage infectsbacterium
Radioactivity inside bacterium
Bacteriophage with sulfur-35 in protein coat
Phage infectsbacterium
No radioactivity inside bacterium
Go to Section
13
Figure 124 Hershey-Chase Experiment
Section 12-1
Bacteriophage with phosphorus-32 in DNA
Phage infectsbacterium
Radioactivity inside bacterium
Bacteriophage with sulfur-35 in protein coat
Phage infectsbacterium
No radioactivity inside bacterium
Go to Section
14
Differences Between DNA and RNA

• DNA
  RNA
• Sugar deoxyribose
  Sugar ribose
• Double strand
  Single strand
• (the helix or twisted ladder)
• Thymine
  Uracil

15
Section Outline
Section 12-2

• 122 DNA Replication
• A. DNA Replication
• 1. Duplicating DNA occurs during interphase
  prior to division
• How Replication Occurs the zipper model
• a. The process begins when an enzyme called
  DNA polymerase attaches to the DNA strand and the
  complementary strands begin to unzip.
• b. Because each strand is complementary,
  each one can be used as a template, or pattern,
  to make a copy of the partner from which it
  separated.

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16
Figure 1211 DNA Replication
Section 12-2
Original strand
DNA polymerase
New strand
Growth
DNA polymerase
Growth
Replication fork
Replication fork
Nitrogenous bases
New strand
Original strand
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17
Prokaryotic Chromosome Structure
Section 12-2
Chromosome
E. coli bacterium
Bases on the chromosome
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18
Figure 12-10 Chromosome Structure of Eukaryotes
Section 12-2
Nucleosome
Chromosome
DNA double helix
Coils
Supercoils
Histones
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19
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 cells 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 cant 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
20
Section Outline
Section 12-3

• 123 RNA and Protein Synthesis
• Types of RNA
• Messenger RNA (mRNA) carries information from
  DNA in the nucleus to the ribosomes where the
  proteins are assembled.
• 2. Ribosomal RNA (rRNA) found in ribosomes and
  help to assemble proteins.
• 3. Transfer RNA (tRNA) transfers the needed
  amino acids from the cytoplasm to the ribosome so
  the proteins dictated by the mRNA can be
  assembled.

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21
Concept Map
Section 12-3
RNA
can be
also called
which functions to
also called
also called
which functions to
which functions to
from
to
to make up
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22
Transcription

• Transcription is the process where the enzyme RNA
  polymerase binds to the DNA and separates the DNA
  strands. Each strand is then used as a template
  from which nucleotides are assembled onto an RNA
  strand.

23
Figure 1214 Transcription
Section 12-3
Adenine (DNA and RNA) Cystosine (DNA and
RNA) Guanine(DNA and RNA) Thymine (DNA
only) Uracil (RNA only)
RNApolymerase
DNA
RNA
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24
Translation see pp. 304 305 in text

• Translation is the process where the information
  from the mRNA is used to produce proteins.
• Proteins are made by joining monomers of amino
  acids (peptides) into long chains of polymers
  called polypeptides. These long chains of
  polypeptides form proteins.

25
Codons and Anticodons

• The genetic code is read three letters (bases) at
  a time. These three triplets of letters
  representing the bases on the mRNA are called
  codons.
• As each codon is read, the tRNA will match its
  complementary anticodon to the codon on the mRNA.
  The anticodons on the tRNA each code for a
  specific amino acid that is used to build the
  long polypeptide chains, forming proteins.

26
Figure 1218 Translation
Section 12-3
Nucleus
Messenger RNA Messenger RNA is transcribed in
the nucleus.
mRNA
Lysine
Phenylalanine
tRNA
Transfer RNA 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.
Methionine
Ribosome
Start codon
mRNA
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27
Figure 1218 Translation (continued)
Section 12-3
The Polypeptide Assembly Line The ribosome
joins the two amino acidsmethionine and
phenylalanineand 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.
Growing polypeptide chain
Ribosome
tRNA
Lysine
tRNA
mRNA
Completing the Polypeptide The process continues
until the ribosome reaches one of the three stop
codons. The result is a growing polypeptide
chain.
mRNA
Translation direction
Ribosome
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28
Figure 1217 The Genetic Code
Section 12-3
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29
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.

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30
Interest Grabber continued
Section 12-4
1. Copy the following information about Protein
X MethioninePhenylalanineTryptophanAsparagine
IsoleucineSTOP. 2. Use Figure 1217 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
31
Section Outline
Section 12-4

• 124 Mutations
• A. Gene Mutations
• B. Chromosomal Mutations

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32
Gene MutationsSubstitution, Insertion, and
Deletion
Section 12-4
Deletion
Substitution
Insertion
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33
Figure 1220 Chromosomal Mutations
Section 12-4
Deletion
Duplication
Inversion
Translocation
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34
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.

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35
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
36
Section Outline
Section 12-5

• 125 Gene Regulation
• A. Gene Regulation An Example
• B. Eukaryotic Gene Regulation
• C. Regulation and Development

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37
Typical Gene Structure
Section 12-5
Promoter(RNA polymerase binding site)
Regulatory sites
DNA strand
Start transcription
Stop transcription
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