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Vocabulary • DNA
• RNA
• Thymine
• Guanine
• Cytosine
• Hydrogen bond
• Adenine
• Uracil
• Replication
• Protein synthesis
• mRNA
• tRNA
• rRNA
• Transcription
• Translation
• Amino acids
• Ribosome
• Peptide bond
• Watson & Crick
• Chromatin
• histones
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Copyright Pearson Prentice Hall
Griffith and Transformation
Griffith and Transformation
In 1928, British scientist Fredrick Griffith was
trying to learn how certain types of bacteria
caused pneumonia.
He isolated two different strains of pneumonia
bacteria from mice and grew them in his lab.
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Griffith and Transformation
Griffith made two observations:
(1) The disease-causing strain of
bacteria grew into smooth colonies on
culture plates.
(2) The harmless strain grew into
colonies with rough edges.
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Griffith and Transformation
Griffith's Experiments
Griffith set up four
individual experiments.
Experiment 1: Mice
were injected with the
disease-causing strain
of bacteria. The mice
developed pneumonia
and died.
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Griffith and Transformation
Experiment 2: Mice
were injected with the
harmless strain of
bacteria. These mice
didn’t get sick.
Harmless bacteria
(rough colonies)
Lives
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Griffith and Transformation
Experiment 3: Griffith
heated the disease-
causing bacteria. He
then injected the heat-
killed bacteria into the
mice. The mice
survived.
Heat-killed disease-
causing bacteria (smooth
colonies)
Lives
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Griffith and Transformation
Experiment 4: Griffith mixed his heat-killed, disease-causing bacteria with live, harmless bacteria and injected the mixture into the mice. The mice developed pneumonia and died.
Live disease-
causing bacteria
(smooth colonies)
Dies of pneumonia
Heat-killed disease-
causing bacteria
(smooth colonies)
Harmless bacteria
(rough colonies)
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Griffith and Transformation
Griffith concluded that the heat-killed bacteria passed their disease-causing ability to the harmless strain.
Live disease-
causing bacteria
(smooth colonies)
Heat-killed disease-
causing bacteria
(smooth colonies)
Harmless bacteria
(rough colonies)
Dies of pneumonia
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Griffith and Transformation
Transformation
Griffith called this process transformation
because one strain of bacteria (the harmless
strain) had changed permanently into another (the
disease-causing strain).
Griffith hypothesized that a factor must contain
information that could change harmless bacteria
into disease-causing ones.
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Avery and DNA
Avery and DNA
Oswald Avery repeated Griffith’s work
to determine which molecule was most
important for transformation.
Avery and his colleagues made an
extract from the heat-killed bacteria that
they treated with enzymes.
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Avery and DNA
The enzymes destroyed proteins,
lipids, carbohydrates, and other
molecules, including the nucleic acid
RNA.
Transformation still occurred.
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Avery and DNA
Avery and other scientists repeated the
experiment using enzymes that would
break down DNA.
When DNA was destroyed,
transformation did not occur. Therefore,
they concluded that DNA was the
transforming factor.
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Avery and DNA
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.
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The Hershey-Chase Experiment
The Hershey-Chase Experiment
Alfred Hershey and Martha Chase studied
viruses—nonliving particles smaller than a cell
that can infect living organisms.
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The Hershey-Chase Experiment
Bacteriophages
A virus that infects bacteria is known as a
bacteriophage.
Bacteriophages are composed of a DNA or
RNA core and a protein coat.
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The Hershey-Chase Experiment
They grew viruses in cultures
containing radioactive isotopes of
phosphorus-32 (32P) and sulfur-35 (35S).
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The Hershey-Chase Experiment
If 35S was found in the bacteria, it would
mean that the viruses’ protein had been
injected into the bacteria.
Bacteriophage with
suffur-35 in protein coat
Phage infects
bacterium No radioactivity
inside bacterium
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The Hershey-Chase Experiment
If 32P was found in the bacteria, then it was
the DNA that had been injected.
Bacteriophage with
phosphorus-32 in DNA Phage infects
bacterium Radioactivity
inside bacterium
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The Hershey-Chase Experiment
If 32P was found in the bacteria, then it was
the DNA that had been injected.
Bacteriophage with
phosphorus-32 in DNA Phage infects
bacterium Radioactivity
inside bacterium
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The Hershey-Chase Experiment
Nearly all the radioactivity in the bacteria was
from phosphorus (32P).
Hershey and Chase concluded that the
genetic material of the bacteriophage was
DNA, not protein.
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12–1 DNA
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The Components and Structure of DNA
The Components and Structure of DNA
DNA is made up of nucleotides.
A nucleotide is a monomer of nucleic acids made
up of:
•Deoxyribose – 5-carbon Sugar
•Phosphate Group
•Nitrogenous Base
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12–1 DNA
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The Components and Structure of DNA
There are four kinds of bases in in DNA:
• adenine
• guanine
• cytosine
• thymine
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12–1 DNA
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The Components and Structure of DNA
Chargaff's Rules
Erwin Chargaff discovered that:
• The percentages of guanine [G] and cytosine
[C] bases are almost equal in any sample of
DNA.
• The percentages of adenine [A] and thymine
[T] bases are almost equal in any sample of
DNA.
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12–1 DNA
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The Components and Structure of DNA
X-Ray Evidence
Rosalind Franklin used X-ray
diffraction to get information
about the structure of DNA.
She aimed an X-ray beam at
concentrated DNA samples
and recorded the scattering
pattern of the X-rays on film.
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12–1 DNA
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The Components and Structure of DNA
The Double Helix
Using clues from Franklin’s pattern, James
Watson and Francis Crick built a model that
explained how DNA carried information and
could be copied.
Watson and Crick's model of DNA was a
double helix, in which two strands were
wound around each other.
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12–1 DNA
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The Components and Structure of
DNA
DNA Double Helix
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12–1 DNA
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The Components and Structure of
DNA
Watson and Crick discovered that hydrogen bonds
can form only between certain base pairs—adenine
and thymine, and guanine and cytosine.
This principle is called base pairing.
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Continue to: Click to Launch:
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12–1
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12–1
Avery and other scientists discovered that
a. DNA is found in a protein coat.
b. DNA stores and transmits genetic
information from one generation to the next.
c. transformation does not affect bacteria.
d. proteins transmit genetic information from
one generation to the next.
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12–1
The Hershey-Chase experiment was based on
the fact that
a. DNA has both sulfur and phosphorus in its
structure.
b. protein has both sulfur and phosphorus in
its structure.
c. both DNA and protein have no phosphorus
or sulfur in their structure.
d. DNA has only phosphorus, while protein
has only sulfur in its structure.
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12–1
DNA is a long molecule made of monomers
called
a. nucleotides.
b. purines.
c. pyrimidines.
d. sugars.
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12–1
Chargaff's rules state that the number of
guanine nucleotides must equal the number of
a. cytosine nucleotides.
b. adenine nucleotides.
c. thymine nucleotides.
d. thymine plus adenine nucleotides.
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12–1
In DNA, the following base pairs occur:
a. A with C, and G with T.
b. A with T, and C with G.
c. A with G, and C with T.
d. A with T, and C with T.
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12-2 Chromosomes and DNA Replication
12–2 Chromosomes and DNA Replication
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Many eukaryotes have 1000 times the
amount of DNA as prokaryotes.
Eukaryotic DNA is located in the cell
nucleus inside chromosomes.
The number of chromosomes varies
widely from one species to the next.
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Chromosome Structure
Eukaryotic chromosomes contain DNA and
protein, tightly packed together to form chromatin.
Chromatin consists of DNA tightly coiled around
proteins called histones.
DNA and histone molecules form nucleosomes.
Nucleosomes pack together, forming a thick fiber.
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Eukaryotic Chromosome Structure
Chromosome
Supercoils
Nucleosome
DNA
double
helix
Histones
Coils
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Duplicating DNA
Before a cell divides, it duplicates its DNA in a
process called replication.
Replication ensures that each resulting cell will
have a complete set of DNA.
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During DNA replication, the DNA molecule separates into two strands, then produces two new complementary strands following the rules of base pairing. Each strand of the double helix of DNA serves as a template for the new strand.
The site of replication is called the replication fork.
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Nitrogen Bases
Replication Fork
DNA Polymerase
Replication Fork
Original strand New Strand
Growth
Growth
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How Replication Occurs
DNA replication is carried out by enzymes that
―unzip‖ a molecule of DNA. This unzipping occurs
when the Hydrogen bonds between base pairs are
broken and the two strands of DNA unwind.
The principle enzyme involved in DNA replication
is DNA polymerase because it joins individual
nucleotides to produce a DNA molecule (polymer).
It also helps to ensure that each molecule is a
perfect copy of the original DNA.
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12–2
In prokaryotic cells, DNA is found in the
a. cytoplasm.
b. nucleus.
c. ribosome.
d. cell membrane.
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12–2
The first step in DNA replication is
a. producing two new strands.
b. separating the strands.
c. producing DNA polymerase.
d. correctly pairing bases.
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12–2
A DNA molecule separates, and the sequence
GCGAATTCG occurs in one strand. What is the
base sequence on the other strand?
a. GCGAATTCG
b. CGCTTAAGC
c. TATCCGGAT
d. GATGGCCAG
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12-3 RNA and Protein Synthesis
12–3 RNA and Protein Synthesis
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Genes are coded DNA instructions that
control the production of proteins.
Genetic messages can be decoded by
copying part of the nucleotide
sequence from DNA into RNA.
RNA contains coded information for
making proteins.
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The Structure of RNA
There are three main differences between RNA and DNA:
a.The sugar in RNA is ribose instead of deoxyribose.
b.RNA is generally single-stranded.
c.RNA contains uracil in place of thymine.
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Types of RNA
There are three main types of RNA:
a.messenger RNA
b.ribosomal RNA
c.transfer RNA
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Messenger RNA (mRNA) carries copies of
instructions for assembling amino acids
into proteins.
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Ribosomes are made up of proteins and
ribosomal RNA (rRNA).
Ribosome
Ribosomal RNA
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During protein construction, transfer RNA
(tRNA) transfers each amino acid to the
ribosome.
Amino acid
Transfer RNA
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DNA
molecule
DNA strand
(template) 3
TRANSCRIPTION
Codon
mRNA
TRANSLATION
Protein
Amino acid
3 5
5
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Transcription (takes place in nucleus)
Promoters: This is a region of DNA that
that indicates to an enzyme where to bind to
make RNA
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RNA
RNA polymerase
DNA
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RNA Editing
• Introns –
sequences of
mRNA NOT
involved in coding
for proteins
• Exons – expressed
sequences of
mRNA
Copyright Pearson Prentice Hall
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The Genetic Code
The genetic code is the ―language‖ of mRNA
instructions.
The code is written using four ―letters‖ (the bases:
A, U, C, and G).
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A codon consists of three consecutive
nucleotides on mRNA that specify a
particular amino acid.
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Nucleus
mRNA Copyright Pearson Prentice Hall
Translation
Translation is the decoding of an mRNA
message into a polypeptide chain
(protein).
Translation takes place on ribosomes.
During translation, the cell uses information
from messenger RNA to produce proteins.
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Lysine tRNA Phenylalanine
Methionine
Ribosome
mRNA Start codon
The ribosome binds new tRNA molecules
and amino acids as it moves along the
mRNA.
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Protein Synthesis
tRNA
Ribosome
mRNA
Lysine
Translation direction
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The process continues until the ribosome reaches
a stop codon.
Polypeptide
Ribosome
tRNA
mRNA
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DNA
mRNA
Protein
Codon Codon Codon
Codon Codon Codon
mRNA
Alanine Arginine Leucine
Amino acids within
a polypeptide
Single strand of DNA
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12–3
The role of a master plan in a building is similar
to the role of which molecule?
a. messenger RNA
b. DNA
c. transfer RNA
d. ribosomal RNA
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12–3
A base that is present in RNA but NOT in DNA is
a. thymine.
b. uracil.
c. cytosine.
d. adenine.
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12–3
The nucleic acid responsible for bringing
individual amino acids to the ribosome is
a. transfer RNA.
b. DNA.
c. messenger RNA.
d. ribosomal RNA.
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12–3
A region of a DNA molecule that indicates to an
enzyme where to bind to make RNA is the
a. intron.
b. exon.
c. promoter.
d. codon.
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A codon typically carries sufficient information to
specify a(an)
a. single base pair in RNA.
b. single amino acid.
c. entire protein.
d. single base pair in DNA.
Copyright Pearson Prentice Hall
12–3
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Mutations are changes in the genetic
material.
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Kinds of Mutations
Kinds of Mutations
Mutations that produce changes in a single gene
are known as gene mutations.
Mutations that produce changes in whole
chromosomes are known as chromosomal
mutations.
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Kinds of Mutations
Gene Mutations
Gene mutations involving a change in one or a
few nucleotides are known as point mutations
because they occur at a single point in the DNA
sequence.
Point mutations include substitutions, insertions,
and deletions.
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Kinds of Mutations
Substitutions
usually affect
no more than a
single amino
acid.
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Kinds of Mutations
The effects of insertions or deletions are
more dramatic.
The addition or deletion of a nucleotide
causes a shift in the grouping of codons.
Changes like these are called frameshift
mutations.
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Kinds of Mutations
In an insertion, an
extra base is
inserted into a
base sequence.
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Kinds of Mutations
In a deletion, the loss of a single base is
deleted and the reading frame is shifted.
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Kinds of Mutations
Chromosomal Mutations
Chromosomal mutations involve changes in the
number or structure of chromosomes.
Chromosomal mutations include deletions,
duplications, inversions, and translocations.
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Kinds of Mutations
Deletions involve the loss of all or part of a
chromosome.
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Kinds of Mutations
Duplications produce extra copies of parts of a
chromosome.
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Kinds of Mutations
Inversions reverse the direction of parts of
chromosomes.
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Kinds of Mutations
Translocations occurs when part of one
chromosome breaks off and attaches to another.
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Significance of Mutations
Significance of Mutations
Many mutations have little or no effect on gene
expression.
Some mutations are the cause of genetic
disorders.
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12–4
A mutation in which all or part of a chromosome
is lost is called a(an)
a. duplication.
b. deletion.
c. inversion.
d. point mutation.
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12–4
A mutation that affects every amino acid
following an insertion or deletion is called a(an)
a. frameshift mutation.
b. point mutation.
c. chromosomal mutation.
d. inversion.
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12–4
A mutation in which a segment of a chromosome
is repeated is called a(an)
a. deletion.
b. inversion.
c. duplication.
d. point mutation.
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12–4
The type of point mutation that usually affects
only a single amino acid is called
a. a deletion.
b. a frameshift mutation.
c. an insertion.
d. a substitution.