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Chapter 12
DNA & RNA
I.DNA
 A. Griffith & Transformation
 Frederick Griffith was trying to figure out how bacteria
made people sick-how they cause a certain type of
pneumonia.
 He isolated 2 strains(types) from mice-both cultured
well,but only one caused pneumonia.The culture of the
disease causing bacteria were
__________________colonies while the other was
rough.
smooth

1-Griffith’s experiments (1928)
 Mice injected w/ disease –causing strain got sick
and died and nothing happened if injected w/other
strain…He wondered if the disease-causing type
made a toxin…?
 So he took some of disease strain and heated to kill
bacteria and then injected into mice….mice survived
suggesting it was not a toxin producing disease
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
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
Lives
Lives
Control
(no growth)
Harmless bacteria
(rough colonies)
Dies of pneumonia
Live, disease-causing
bacteria (smooth colonies)




2-Transformation
He mixed his heat –killed w/ live harmless bacteria and
injected into mice…..________________________
Somehow the disease –causing strain passed their
disease capacity to harmless bacteria….. disease –
causing strain found in lungs
He called this changing of one bacteria by the genes of
another _____________________....Thus a
factor(gene) from heat killed disease –causing strain
was passed on.
Mice developed
pneumonia
transformation
B. Avery & DNA
 Team of scientists lead by Avery in 1944 repeated
Griffith’s experiment in order to determine which
molecule was responsible for the transformation.
 They made an extract from the heat-killed bacteria
and treated it w/enzymes that kill proteins,lipids and
other molecules,inc. RNA
Avery cont’d
transformation
 ____________________still occurred so the above
molecules were not responsible for transformation
 They repeated the experiment but used enzymes that
kill____________, stopping transformation…. DNA
 Therefore ________caused the transformation and
thus stores and transmits genetic info
C. The Hershey –Chase Experiment
 1952-Alfred Hershey and Martha Chase studied
viruses-disease-causing particles smaller than a cell.
 ______________________-virus that infects
bacteria.They have a DNA or RNA core and a protein
coat…They attach to the surface of a bacterium and
inject genetic info into cell.The viral genes act to
produce many new bacteriophages and eventually
destroy bacterial cell,w/_____________bursting out.
bacteriophage
viruses
 They grew viruses in cultures containing
_________________________________,mixed them
w/bacteria and waited a few min. for viruses to inject
genetic material.
 Then they separated the bacteria from the viruses
and tested bacteria for radioactive marker…..nearly
all the radioactivity was P-32-found in _________---thus concluding it was the genetic material was
DNA !
Radioactive
markers
DNA
Figure 12–4 Hershey-Chase
Experiment
Section 12-1
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
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
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 Components and Structure of
DNA
 Scientists questioned how the DNA molecule could
do three things 1)carry info from 1 generation to the
next 2)putting that info to work and 3)could be easily
copied
 DNA is a long molecule made of units called
___________________________________________-
nucleotides
The nucleotide is made of 3 basic
parts:______________________(sugar),
a phosphate group and
a_________________________________
deoxyribose
Nitrogenous base
 2 nitrogenous bases are purines(have 2
rings):___________________________(A)and_______
(G)
 2 other nitrogenous bases are pyrimidines (have 1
ring):____________________(C)and
____________________________(T)
Adenine ,guanine
Cytosine and
thymine
--backbone made by sugar and phosphate w/ bases sticking
out sideways
Figure 12–5 DNA
Nucleotides
Section 12-1
Purines
Adenine
Guanine
Phosphate
group
Pyrimidines
Cytosine
Thymine
Deoxyribose

1-_______________________Rules-discovered that
%’s of Cytosine and guanine were almost equal in
DNA and the same was true for adenine and
thymine….Thus A pairs w/T and C w/ G-BASE
PAIRING
Chargaff’s Rules
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

2- X-ray evidence-1950’s –Rosalind Franklin
used X-ray diffraction to learn about DNA
structure----The scattered X pattern seen begins to
show the __________-partial TWISTED
STRUCTURE of DNA
helix
 3---Double helix_


Watson and Crick -2 strands wound around each
other---like the twisted ladder or spiral staircase
Strands held together by H-bonds
Figure 12–7 Structure of
DNA
Section 12-1
Nucleotide
Hydrogen
bonds
Sugar-phosphate
backbone
Key
Adenine (A)
Thymine (T)
Cytosine (C)
Guanine (G)
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.
Section 12-2
1.
On a sheet of paper, draw a curving or zigzagging 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?
II. Chromosomes & DNA Replication
A-DNA & Chromosomes
In cytoplasm in prokaryotes
In _______________________found in cell
nucleus in the form of a number of
chromosomes(46 humans,8 Drosophilia and
22 Sequoia trees)
eukaryotes
 1--DNA length
 1.6 mm in E.coli(has 4,639,221 base pairs)--obviously it must be tightly folded

2-Chromosome Structure
 Eukaryotic cells have about 1000 times as many
base pairs of DNA than a bacterium
 Humans cells have ~ 1 m DNA
 Eukaryotic chromosomes contain DNA and a
protein ,which together make
_____________________-consisting of DNA
tightly packed around proteins called histones
chromatin
DNA and histone together make
beadlike_____________________________
Nucleosomes pack together to make thick
fibers,drawn together during mitosis…also
separating
 Role of nucleosomes-fold great lengths of DNA into
tiny spaces
nucleosomes
Prokaryotic Chromosome Structure
Section 12-2
Chromosome
E. coli bacterium
Bases on the chromosome
Figure 12-10 Chromosome Structure
of Eukaryotes
Section 12-2
Chromosome
Nucleosome
DNA
double
helix
Coils
Supercoils
Histones
B. DNA Replication





Each strand of DNA double helix has all the info
to___________________________by base pairing
Strands are complementary
In prokaryotes,this begins @single point and
proceeds-often in 2 directions
In Eukaryotes,DNA replication begins @ 100’s of
places,going both directions until complete
__________________________is where replication
occurs
Reconstruct the
other half
Replication fork

1-Duplicating DNA
 __________________________or duplication of
DNA happens before cell division---ensuring
each cell has a complete set of DNA molecules
 Each strand of a double helix serves as a
_____________________or model for new strand
 A pairs w/ T and C w/ G
template
replication

2-How Replication Occurs
 Carried out by a series of enzymes that unzip a
molecule
 ____________________________________ joins
individual nucleotides to make a DNA
molecule….also proof reads the new strands
DNA
polymerase
Figure 12–11 DNA
Replication
Section 12-2
New strand
Original
strand
DNA
polymerase
Growth
DNA
polymerase
Growth
Replication
fork
Replication
fork
New strand
Original
strand
Nitrogenous
bases
III. RNA & Protein Synthesis

The double helix structure explains how DNA is
copied,but not how a gene works_______________are coded DNA instructions that
control the production of protein in the cell.

A) The structure of RNA
 Long chain of nucleotides
 3 main differences between DNA & RNA:
 1--Sugar is _________________
 2---Generally single-stranded
 3---RNA contains ________________(U) in
place of thymine (T)
uracil
genes
ribose
B. Types of RNA
Protein
synthesis

Main job=_________________-ie the assembly of amino
acids into proteins
 3 Types:
 ____________________(mRNA)-carry copies for
instructions from DNA to rest of cell
 ____________________(rRNA)-type of RNA that helps
make up ribosomes,where proteins assembled
 ________________(tRNA)transfers each amino acid to
the ribosome as it is coded for on mRNA.
messenger
ribosomal
Transfer
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
tRNA
which functions
to
Bring
amino acids to
ribosome
C. Transcription-produces RNA molecules by copying
part of nucleotide sequence of DNA into a
complementary sequence in RNA
 Requires enzyme known as
_______________________________________binds to DNA and separates DNA strands.Then
uses one strand as template to make RNA
 The enzyme only binds to areas known as
promoters-signals that indicate where to make
RNA.Similar signals tell where to stop
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)
RNA
polymerase
DNA
RNA
D. RNA editing
 ________________________ in eukaryotic genes
,sequences of nucleotides that ARE NOT
involved in coding for proteins
 _______________________-DNA sequence that
does code for protein
exons
introns
E. Genetic Code
polypeptide
 ______________________-chain of amino
acids=proteins
codon
 _________________-3 consecutive nucleotides
that specify a specific amino acid
 Example –UCGCACGGU reads UCG_CAC_GGU
and codes for Serine-Histidine-Glycine
The Genetic Code
Section 12-3
Universal code
64 possible 3 base codons
AUG can specify methionine or start
codon
3 stop codons that do not code for an
amino acid
F. Translation
ribosome
 ______________________reads the instructions
for the order in which amino acids should be joined
by reading mRNA
translation
 ____________________________is the decoding
of an mRNA message into a polypeptide(protein)
 Before translation occurs,mRNA is transcribed from
DNA and released into
cytoplasm
__________________________.
 Translation begins when mRNA molecule in
cytoplasm attaches to a _____________________.
ribosome
As each codon of the mRNA moves through the
moves through the
tRNA
ribosome,_____________brings in the
proper,indicated amino acid and transferred to
polypeptide chain
Each tRNA carries one kind of amino acid
__________________ is a group of 3 bases on a
tRNA that are complementary to a mRNA codon
Ribosome forms a _________________bond
between amino acids and breaks tRNA bond
releasing it
Protein keeps growing until ribosome reaches
stop codon on mRNA
peptide
anticodon
Figure 12–18 Translation
Section 12-3
Figure 12–18 Translation (continued)
Section 12-3
Changes in genetic material
Mutations=________________________
Gene mutation




A.---Kinds of Mutations

1)

________________________________-changes in a
single gene
_____________________________________-changes in 1 or
a few nucleotides-@ a single point in DNA-includes
substitutions,insertions and deletions
Substitutions usually affect no more than 1 amino acid
____________________________________-insertions or
deletions where the reading frame of the codon message is
changed-can VERY much alter or even stop the function of
a protein
Point
mutation
Frameshift
mutation




 2)Chromosomal Mutations-change in the # or
structure of chromosomes-can change the
location of genes on chromosomes and /or
number of copies of some genes.
4 types-1)Deletions-loss of all or part of a
chromosome
2)__________________-extra copies of a part of a
chromosome
3)________________reverse directions of parts of
chromosomes
4)____________-part of one chromosome breaks
off and attaches to another
translocations
duplication
inversions
Gene Mutations: Substitution, Insertion,
and Deletion
Section 12-4
Substitution
Deletion
Insertion
Figure 12–20 Chromosomal
Mutations
Section 12-4
Deletion
Duplication
Inversion
Translocation
B. Significance of Mutations
 Many have no effect
 Harmful effects include genetic disorders and cancer
 ________________________-contains extra set of
chromosomes-bad in most cases but often helpful in
PLANTS.
polyploidy
V. Gene Regulation





operon
Only a fraction of a gene expressed at one time
___________________-group of genes that
operate together
________________-where repressor binds operon
(when it)is turned off
Operons not usually found in eukaryotes-these
genes are usually controlled individually and
regulation more complex---mainly because of cell
specialization
Hox genes-control differentiation of cells and
tissues in the embryo
operator
Typical Gene Structure
Section 12-5
Regulatory
sites
Promoter
(RNA polymerase
binding site)
Start transcription
DNA strand
Stop transcription
Karyotypes