Download DNA Double Helix

Biology
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12–1 DNA
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Bell Work
4-20-2015
1.
What is the control center of a cell?
2.
What are the 3 critical things genes were known to do by the
early scientist? (p. 291)
Learning Target
I can explain how scientist discovered the relationship between
genes and DNA.
Learning Target
I can explain how scientist discovered the relationship
between genes and DNA.
Agenda:
1.
Bell Work / LT
2.
Biologist Timeline
??????
What was Fredrick Griffith trying to
learn?
Why was he trying to learn how
bacteria made people sick?
Why is it important to learn how
bacteria causes diseases?
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.
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.
Who can describe Griffiths first experiment?
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.

Second experiment?
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

Third experiment?
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Griffith and Transformation
Experiment 3: Griffith
heated the diseasecausing bacteria. He then
injected the heat-killed
bacteria into the mice.
The mice survived.
Heat-killed diseasecausing bacteria (smooth
colonies)
Lives

Fourth experiment?
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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.
What did Griffith conclude?
Griffith and Transformation
Griffith concluded
that the heatkilled bacteria
passed their
disease-causing
ability to the
harmless strain.
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What did Griffith call this process of changing one molecule
into another?
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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 diseasecausing strain).
Griffith hypothesized that a factor must contain
information that could change harmless bacteria
into disease-causing ones.
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What did Avery want to determine?
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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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
How did Avery go about this testing?
Avery and DNA
The enzymes destroyed proteins,
lipids, carbohydrates, and other
molecules, including the nucleic acid
RNA.
Transformation still occurred.
What is the next step Avery took?
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.
What was Avery's conclusion?
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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.
What question did Hershey and Chase want answers to?
The
The Hershey-Chase
Hershey-Chase Experiment
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
Wanted to know if genes were made of protein or DNA.
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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How did they go about their experiment?
The Hershey-Chase Experiment
They grew viruses in cultures
containing radioactive isotopes
of phosphorus-32 (32P) and
sulfur-35 (35S).
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
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
What did they find in the bacteria?
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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.
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
 Phosphate
– 5-carbon Sugar
Group
 Nitrogenous
Base
The Components and Structure of DNA
There are four kinds
of bases in in DNA:
 adenine
 guanine
 cytosine
 thymine
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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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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 Xrays on film.
The Double Helix
The Components and Structure of DNA
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.
The Components and Structure of DNA
DNA Double Helix
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.
Bell Work
4-21-2015
1.
What does a double helix look like?
2.
Use the scissors on your desk to cut out the pieces for a
double helix.
Learning Target.
I can explain a double helix.
Learning Target.
I can explain a double helix.
Agenda
1.
Bell Work / LT
2.
Plickers
3.
Activity
4.
Discussion
Bell Work
1.
2.
3.
4-22-2015
What does a double helix look like?
What is the pattern for base pairing?
Name the molecules that make up the sides of the DNA
Ladder.
Learning Target
I can explain the structure of a double helix.
Learning Target
I can explain the structure of a double helix.
Agenda
1.
Bell Work / LT
2.
Review Assignment
3.
Activity
4.
Plickers
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12–1
Avery and other scientists discovered that

DNA is found in a protein coat.

DNA stores and transmits genetic information from one
generation to the next.

transformation does not affect bacteria.

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

DNA has both sulfur and phosphorus in its structure.

protein has both sulfur and phosphorus in its structure.

both DNA and protein have no phosphorus or sulfur in their structure.

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

nucleotides.

purines.

pyrimidines.

sugars.
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12–1
Chargaff's rules state that the number of guanine nucleotides
must equal the number of

cytosine nucleotides.

adenine nucleotides.

thymine nucleotides.

thymine plus adenine nucleotides.
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12–1
In DNA, the following base pairs occur:

A with C, and G with T.

A with T, and C with G.

A with G, and C with T.

A with T, and C with T.
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12-2 Chromosomes and DNA Replication
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Bell Work
4-21-2015
1.
Considering your knowledge of DNA, what might happen
if bases paired incorrectly?
2.
What is the pattern for base pairing?
3.
Name the molecules that make up the sides of the DNA
Ladder.
Learning Target
I can explain DNA replication.
Learning Target
I can explain DNA replication.
Agenda
1.
Bell Work / LT
2.
Discussion of RNA
3.
Assignment
4.
Quizlet
Research
Where is DNA found in both prokaryotic and eukaryotic
cells?
DNA and Chromosomes
DNA and Chromosomes
In prokaryotic cells, DNA is
located in the cytoplasm.
Most prokaryotes have a single
DNA molecule containing
nearly all of the cell’s genetic
information.
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DNA and Chromosomes
Chromosome
E. Coli Bacterium
Bases on the
Chromosomes
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DNA and Chromosomes
Many eukaryotes have 1000 times
the amount of DNA as prokaryotes.
Eukaryotic DNA is located in the cell
nucleus inside chromosomes.
 number
of chromosomes varies
widely from one species to the
next.
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DNA and Chromosomes
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
fiber.
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pack together, forming a thick
DNA and Chromosomes
Eukaryotic Chromosome Structure
Chromosome
Nucleosome
DNA
double
helix
Coils
Supercoils
Histones
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Research
What is DNA Replication?
https://www.youtube.com/watch?v=27TxKoFU2Nw
DNA Replication
DNA Replication
Each strand of the DNA double helix
has all the information needed to
reconstruct the other half by the
mechanism of base pairing.
In most prokaryotes, DNA
replication begins at a single point
and continues in two directions.
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DNA Replication
In eukaryotic chromosomes, DNA
replication occurs at hundreds of
places. Replication proceeds in both
directions until each chromosome is
completely copied.
The sites where separation and
replication occur are called
replication forks.
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DNA Replication
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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DNA Replication
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.
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DNA Replication
New Strand
Original strand
Nitrogen Bases
Growth
Growth
Replication Fork
Replication Fork
DNA Polymerase
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Research
How does replication occur?
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How Replication Occurs
DNA replication is carried out by
enzymes that “unzip” a
molecule of DNA.
Hydrogen bonds between base
pairs are broken and the two
strands of DNA unwind.
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DNA Replication
The principal enzyme involved in DNA
replication is…. DNA polymerase

joins individual nucleotides to
produce a DNA molecule and then
“proofreads” each new DNA strand.
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12–
2
In prokaryotic cells, DNA is found in the

cytoplasm.

nucleus.

ribosome.

cell membrane.
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12–
2
The first step in DNA replication is

producing two new strands.

separating the strands.

producing DNA polymerase.

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?

GCGAATTCG

CGCTTAAGC

TATCCGGAT

GATGGCCAG
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12–
2
In addition to carrying out the replication of DNA, the enzyme
DNA polymerase also functions to

unzip the DNA molecule.

regulate the time copying occurs in the cell cycle.

“proofread” the new copies to minimize the number of
mistakes.

wrap the new strands onto histone proteins.
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12–
2
The structure that may play a role in regulating how genes
are “read” to make a protein is the

coil.

histone.

nucleosome.

chromatin.
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12–3 RNA and Protein Synthesis
12-3 RNA and Protein Synthesis
Copyright Pearson Prentice Hall
Bell Work
4-21-2015
1.
What might you compare the looks of a
supercoiled nucleosome to that you are
familiar?
2.
What is chromatin?
3.
What is the job of a nucleosome?
Learning Target
I can explain the how RNA differs from DNA.
Learning Target
I can explain the how RNA differs from DNA.
Agenda
1.
Bell Work / LT
2.
Discussion of RNA
3.
Activity / Assignment
4.
Plickers
5.
Quizlet
Research

How does a gene Work?
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12–3 RNA and Protein
Synthesis
How does a gene Work?
1. Genes are coded DNA instructions that
control the production of proteins.
2. Genetic messages can be decoded by
copying part of the nucleotide sequence
from DNA into RNA.
3. RNA contains coded information for
making proteins.
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Research

What is the structure of RNA compare to DNA?
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The Structure of RNA
The Structure of RNA
There are three main differences between RNA and
DNA:
The
sugar in RNA is ribose instead of
deoxyribose.
RNA
is generally single-stranded.
RNA
contains uracil in place of thymine.
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Research
What are the 3 types of RNA?
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Types of RNA
Types of RNA
There are three main types of
RNA:
messenger
ribosomal
transfer
RNA
RNA
RNA
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Types of RNA
Messenger RNA (mRNA) carries copies of instructions for assembling
amino acids into proteins.
***Serve as “messengers” from DNA to the rest of the cell
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Types of RNA
Ribosomes are made up of proteins and ribosomal RNA (rRNA).
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Types of RNA
During protein
construction,
transfer RNA (tRNA)
transfers each amino
acid to the ribosome.
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Research

Describe Transcription.
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Transcription
DNA is copied in the form of a
complementary sequence called
RNA
Requires RNA polymerase to bind to
DNA and separate the DNA strands
as a template to assemble the
nucleotides into another DNA strand
This first process is called
transcription.
The process begins at a section of
DNA called a promoter, which has
specific base sequence that signal
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where Copyright
to start
Protein Synthesis
DNA
molecule
DNA strand
(template)
5
3
TRANSCRIPTION
mRNA
5
3
Codon
TRANSLATION
Protein
Amino acid
Transcription
RNA
RNA polymerase
DNA
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Research
What are the functions of introns and exons?
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RNA Editing
RNA Editing
Some DNA within a gene is not needed to
produce or code for a protein. These areas
are called introns.
The DNA sequences
that code for proteins
are called exons.
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RNA Editing
The introns are cut
out of RNA
molecules…scientist
have no idea why…
The exons are the
spliced together to
form mRNA.
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Exon Intron
DNA
Pre-mRNA
mRNA
Cap
Tail
Bell Work
4-22-2015
1.
Compare the DNA code to something you need a code to
in your daily life.
2.
What are the 3 types of RNA?
3.
Explain transcription.
Learning Target
I can explain the genetic code.
Learning Target
I can explain the genetic code.
Agenda
1.
Bell Work / LT
2.
Plickers
3.
Discussion
4.
Activity
Research
What is the genetic code?
The Genetic Code
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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Research
What is a codon?
The Genetic Code
A codon consists of three consecutive
nucleotides on mRNA that specify a
particular amino acid.
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The Genetic Code
There are 64
possible
base
codons…
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Research

What is translation and where does it take place?
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 and tell what order
they should be listed in on the polypeptide.
Nucleus
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mRNA
Translation
The ribosome binds new tRNA molecules and amino
acids as it moves along the mRNA.
Phenylalanine
Methionine
Ribosome
mRNA
Start
codon
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tRNA
Lysine
Translation
Lysine
tRNA
Protein Synthesis
Translation direction
mRNA
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Ribosome
Translation
The process continues until the ribosome reaches a
stop codon.
Polypeptide
Ribosome
tRNA
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mRNA
Codon
Genes and Proteins
Codon Codon
DNA
Single strand of DNA
mRNA
Codon Codon Codon
Protein
mRNA
Alanine Arginine Leucine
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Amino acids within
a polypeptide
Bell Work
4-23-2015
1.
Are enzymes tossed away or reused?
2.
Log onto Quizlet and Study for Friday’s Vocabulary Formative.
Learning Target
I can explain DNA structure and Replication.
Learning Target
I can explain DNA structure and Replication.
Agenda
1.
Bell Work / LT
2.
Quizlet
3.
Activity
4.
Plickers
DNA Replication Enzyme Wrap Up
12–
3
The role of a master plan in a building is similar to the role of
which molecule?

messenger RNA

DNA

transfer RNA

ribosomal RNA
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12–
3
A base that is present in RNA but NOT in DNA is

thymine.

uracil.

cytosine.

adenine.
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12–
3
The nucleic acid responsible for bringing individual amino
acids to the ribosome is

transfer RNA.

DNA.

messenger RNA.

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

intron.

exon.

promoter.

codon.
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12–
3
A codon typically carries sufficient information to specify
a(an)

single base pair in RNA.

single amino acid.

entire protein.

single base pair in DNA.
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