Download DNA, RNA, and Proteins

2/6/17
Section 1: The Structure of DNA
DNA, RNA, and
Proteins
Chapter 13
—  Gene: A segment of DNA that is located
in a chromosome and that codes for a
specific hereditary trait
—  DNA: Deoxyribonucleic Acid; the material
that contains the information that
determines inherited characteristics
I. DNA: The Genetic Material
—  Nucleotide: A subunit in a nucleic acid
chain, that consists of a sugar, phosphate
and nitrogenous base.
A. Traits are passed from parents to offspring
B. Genes are instructions for inherited traits
—  Purine: A nitrogenous base that has a
double-ring structure
—  Pyrimidine: A nitrogenous base that has a
single-ring structure
I. DNA: The Genetic Material
C. Genes are made
from DNA
D. DNA is a primary
material that causes
recognizable,
inheritable
characteristics in
related groups of
organisms
II. Searching for Genetic Material
A.  Three major experiments led to the conclusion
that DNA is the genetic material in cells:
1.  Frederick Griffith’s Discovery
of Transformation (1928)
A.  Took 1st steps in figuring
out whether genes are
made of DNA or protein
B.  Worked with Streptococcus
pneumoniae
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3. Griffith’s Experiments
a.  S bacteria caused pneumonia and death
2.  2 Strains
a)  S strain: looks smooth; cause pneumonia
b)  R strain: looks rough; doesn’t cause
when injected into mice.
b.  R bacteria had no visible effect when
injected into mice
pneumonia
3. Griffith’s Experiments
c.  S bacteria were killed by heating. Heat-killed S
bacteria did not harm mice.
d.  Griffith grew live R bacteria after mixing with
heat-killed S bacteria. Mice injected with the
mixture died of pneumonia
4. Griffith’s Conclusions
a.  Genetic material could be transferred
between cells
b.  No one knew this material was DNA
B. Oswald Avery’s Experiments with
Nucleic Acid (1940s)
B. Oswald Avery’s Experiments with
Nucleic Acid (1940s)
1.  Wanted to determine if transforming material
2.  Avery’s Experiment
a.  Used enzymes to destroy each of these
in Griffith’s experiments was protein, RNA or
DNA
molecules in heat killed S bacteria
b.  Found bacteria that were missing protein
and RNA were able to transform R cells
into S cells
c.  Bacteria that were missing DNA did not
transform R cells
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B. Oswald Avery’s Experiments with
Nucleic Acid (1940s)
2.  Avery’s Experiment
B. Oswald Avery’s Experiments with
Nucleic Acid (1940s)
3.  Avery’s Conclusions
a.  DNA is responsible for transformation in
bacteria
C. Hershey-Chase Experiment (1952)
1. DNA or Protein?
a.  Experimented using viruses called
bacteriophages (phage)
b.  Components of a phage
1.  DNA
2.  Protein
2. Hershey-Chase Experiment
2. Hershey-Chase Experiment
a.  Phages with radioactive (green) DNA
infected bacteria
1.  Bacteria became radioactive
2.  DNA entered bacteria
b.  Phages with radioactive (green) protein
infected bacteria
1.  Bacteria did not become radioactive
2.  Protein did not enter bacteria
3. Hershey-Chase Conclusion
a.  Only the DNA of viruses is injected into
bacterial cells
b.  Injected DNA cause bacteria to produce viral
DNA and proteins
c.  DNA is hereditary material
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III. The Shape of DNA
A.  A Winding Staircase
1.  DNA molecule is
shaped like a spiral
staircase and is
composed of two
parallel strands of linked
subunits
2.  Parts of the Nucleotide
Subunits
a.  Nucleotide Components
1.  Phosphate Group
2.  5-carbon sugar
(deoxyribose)
a.  Known as a double
3.  Nitrogen containing base
b.  Backbone made up of
b.  Each strand made up
c.  Bases pair to connect strands
helix
phosphate group and sugar
of linked subunits
called nucleotides
IV. The Information in DNA
A. The information in DNA is contained in the
order of the bases, while base-pairing
structure allows the information to be
copied
B. Nitrogenous Bases
1.  Each nucleotide has the same sugar and
2. Bases are what is different (1 of 4)
a.  Purine (large molecule)
1.  Adenine (A)
2.  Guanine (G)
b.  Pyrimidine (small molecule)
1.  Cytosine (C)
2.  Thymine (T)
phosphate backbone
C. Base-Pairing Rules
D. Complementary Sides
1.  Purine always pairs with Pyrimidine
1.  Base pairs are Complementary
2.  Adenine always pairs with Thymine
2.  Fit together like puzzle pieces
3.  Guanine always pairs with Cytosine
3.  Information on one side is reverse of
information on the other side.
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V. Discovering DNA’s Structure
4. A T C G A T T A C T A G G A
A. Watson and Crick used information from
experiments by Chargaff, Wilkins and
Franklin to determine the 3D structure of
DNA
5. T A G C T A A T G A T C C T
B. Observing Patterns:
Chargaff’s Observations (1949)
B. Observing Patterns:
Chargaff’s Observations (1949)
1.  For each organism he studied
a.  amount of Adenine was equal to amount
of Thymine
b.  amount of Guanine was equal to amount
of Cytosine
2.  Watson and Crick used this information to
determine how bases paired.
C. Using Technology:
Photographs of DNA (1952)
1.  Rosalind Franklin and
Maurice Wilkins
developed high-quality
X-ray diffraction images
of strands of DNA
C. Using Technology:
Photographs of DNA (1952)
2.  X-rays showed
DNA molecule
resembled a tightly
coiled helix and
was composed of 2
chains of
nucleotides
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D. Watson and Crick’s Model of DNA
1.  Built a 3D model
2.  Used information from Chargaff,
Wilkins, and Franklin
Section 2: Replication of DNA
—  DNA Replication: The process of making a
copy of DNA
—  DNA Helicase: An enzyme that unwinds/
unzips the DNA double helix during DNA
replication
—  DNA Polymerase: AN enzyme that
catalyzes the formation of the DNA
Molecule
I. DNA Replication
A.  DNA is made of 2 complementary base pairs
E. Allows 2 exact copies of DNA to be
B.  Adenine always pairs with Thymine
made from the original molecule
C. Guanine always pairs with Cytosine
F.  Process of making a copy of DNA is
D. If strands are separated each can serve as a
DNA replication
pattern for new complementary strands
G. Steps of Replication
1. Unwinding and
separating DNA strands
a. Double Helix unwinds
2. Adding Complementary Bases
b. (Helicase) enzymes
separate DNA strands,
forming Y-shapes
a. At each replication fork, new
nucleotides are added to each side of
the DNA strand (DNA polymerase,
Primase, Ligase)
c. Y-shape at each end of
“unzipping” is called a
replication fork
b. The original 2 strands are unchanged.
Each serves as a template for a new
strand = 2 new strands
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II. Replication
3. Formation of two identical DNA
molecules
a. Each identical double-stranded DNA
molecule is made of one new strand
and one original stand
C.  DNA Polymerase
1.  Protein/enzyme that catalyzes the
formation of the DNA molecule
2.  Also has a “proofreading” function
a.  Helps to reduce errors
A. During replication of DNA, many
proteins/enzymes work together like an
assembly line.
B. DNA Helicase
1. Protein/enzyme unwinds/unzips DNA
during replication
Section 3: RNA and
Gene Expression
—  RNA: Ribonucleic acid; a natural polymer that
is present in all living cells and that plays a role
in protein synthesis
—  Gene Expression: The manifestation of the
genetic material of an organism in the form of
specific traits
Amoeba Sisters DNA Replication (7:58)
—  Transcription: The process of forming a
nucleic acid by using another molecule as a
template
—  Translation: The portion of protein synthesis
that takes place at ribosomes and that uses
the codons in mRNA molecules to specify the
sequence of amino acids in polypeptide chains
I.  DNA provides the original information
from which proteins are made
A.  DNA does not actually make the protein
B.  RNA is essential in taking the genetic
information from DNA and building proteins
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II. An Overview of Gene Expression
A.  Gene expression produces proteins by
transcription and translation
B.  Transcription: DNA to RNA
1.  1st stage of gene expression
2.  Making RNA from information in DNA
3.  Transcription is similar to copying
(transcription) notes from the overhead
(DNA) to your note packet (RNA)
C. Translation: RNA to Protein
1.  2nd Stage of Gene Expression
2.  Uses the information in RNA to make specific
proteins
3.  Translation is similar to translating a sentence
in one language (RNA, the nucleic acid
language) to another language (protein, the
amino acid language)
III. RNA: A Major Player
A.  In cells, three types of RNA complement
DNA and translate the genetic code into
proteins
B.  RNA Versus DNA
1. Similar
a.  Both have nucleic acids
b.  Both have 4 bases
c.  Both carry information
d.  Both have bases adenine, cytosine, and
2. Different
a.  RNA is single stranded / DNA is double
stranded
b.  RNA nucleotides have ribose sugar / DNA
nucleotides have deoxyribose sugar
c.  RNA has a nitrogen base called uracil (U)
instead of DNA’s thymine
guanine
DNA v. RNA
3. DNA Base Pairs
4. RNA Base Pairs
a.  A=T
a.  A=U
b.  C=G
b.  C=G
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C. Types of RNA
mRNA
1.  3 Types of RNA play a role in gene expression
a.  Messenger RNA (mRNA)
1)  Produced when DNA is transcribed in
RNA
2)  Complementary to the DNA sequence of
a gene
3)  mRNA carries instructions for making a
protein from a gene and delivers them to
the site of translation
Types of RNA
b.  Transfer RNA (tRNA)
1)  During translation, tRNA “reads” the mRNA
tRNA
sequence
2)  Translates the mRNA sequence into a
specific sequence of protein subunits or
amino acids
3)  tRNA has amino acids attached
4)  Act as decoders by matching mRNA
sequence and placing amino acids on
protein chains
Types of RNA
c.  Ribosomal RNA (rRNA)
1)  RNA that is found in ribosomes to help
make proteins
IV. Transcription: Reading the Gene
A.  During transcription, the information in a
specific region of DNA (a gene) is transcribed,
or copied into mRNA
B.  Transcription carried
out by protein called
RNA polymerase
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C. Steps of Transcription
1.  Step 1
a.  RNA polymerase binds to the specific DNA
sequence in the gene called the promoter
b.  Promoter site is the start location
2.  Step 2
a.  RNA polymerase unwinds and separates 2
strands of double helix to expose DNA bases
3.  Step 3
a.  RNA polymerase reads the gene
b.  RNA polymerase moves along the bases on
the DNA like a train moves along the track
D. Transcription vs. Replication
1.  Similar
a.  Both use DNA as a template
2.  Different
a.  Transcription: RNA is made from DNA
Steps of Transcription, cont.
3.  Step 3
a.  RNA polymerase reads the gene
b.  RNA polymerase moves along the bases on
the DNA like a train moves along the track
c.  Transcription follows same base pairing rules
as DNA replication except uracil takes the
place of thymine
d.  Forms single strand of RNA
e.  DNA double helix closes up behind the moving
RNA polymerase
f.  RNA polymerase eventually reaches a stop
location
V. The Genetic Code:
Three letter “Words”
A.  A gene is compared to a sentence of words that is first
transcribed and then translated into a protein.
Replication: DNA is made from DNA
b.  Transcription: 1 strand of DNA is used to
make RNA strand
Replication: both strands of DNA are
used to make 2 DNA strands
B. Codons of DNA
Codons of DNA, cont.
1.  Each word is made up of 3 adjacent nucleotide bases
3.  Each codon specifies only one amino acid
called a codon
2.  Codons match 1 of 20 amino acids or act as a start or
4.  Several amino acids have more than one codon
stop signal
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Codons of DNA, cont.
5.  System of matching codons and amino acids is called
Amino Acids to Proteins
the genetic code
6.  Genetic code is based on codons that each represent a
specific amino acid.
VI. Translation: RNA to Proteins
A.  Process of converting the language of RNA into the
language of proteins
B.  Translation occurs in a sequence of steps, involves
three kinds of RNA, and results in a complete
polypeptide
1. Step 1
a.  Amino acid is added to one end of each tRNA
b.  Other end has anticodon
b.  Anticodon is 3-nucleotide sequence that is
complementary to an mRNA codon
c.  After leaving the nucleus, mRNA joins with
ribosome and tRNA
d.  RNA start codon AUG signals the beginning of a
protein chain
e.  tRNA molecule carrying methionine at one end
and the anticodon UAC, at the other, binds to the
start codon
2. Step 2
a.  tRNA molecule that has the correct anticodon
and amino acid binds to the second codon on
the mRNA
b.  Peptide bond forms between the two amino
acids
c.  1st tRNA is released from the ribosome
d.  tRNA leaves its amino acid behind
3. Step 3
a.  Ribosome moves one codon down the
mRNA
b.  Amino acid chain continues to grow as
each new amino acid bonds to the chain
4. Step 4
a.  Process is repeated until a stop codon is
reached
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5. Step 5
C. Repeating Translation
a.  Newly made protein falls off the ribosome
b.  Ribosome is free to begin translation again
with another mRNA
1.  Translation happens quickly and often
2.  Several ribosomes can translate one DNA
strand at a time
a.  This makes several copies of a protein very
quickly
Translation
VII. Complexities of Gene Expression
A.  The relationship between genes and their effect is
complex. Despite the neatness of the genetic code,
every gene cannot be simply linked to a single
outcome
B.  Some genes are expressed at certain times under
certain conditions
C.  Some traits result from the expression of multiple
genes
D.  Final outcome of gene expression is affected by:
1.  The environment of the cell
2.  Presence of other cell
3.  Timing of gene expression
https://www.youtube.com/watch?v=8nQH0GqFn6k&list=PLj8vIYYJwwPnf60rp2QQhVRzq-EFNOU3k&index=5
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