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What is DNA?
Is knowing about DNA important?
Chapter 8 Questions
DNA and Protein Synthesis

Chapter 8
Reading requirements: pages 171 - 186
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Problems (p.193 & 194):
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•
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Date due
•(Recalling) 3-7
•(Reviewing) 1,6,7,9,10
•(Expanding) 6-8
•
•
Focus on DNA…
DNA…

What is DNA?

What does DNA do?

What is DNA composed of?

Where is DNA located?
things you know about DNA
what you think of when you hear the
term, DNA ?
things you want to know about DNA
is it important to know about DNA? Why
or why not?
The macromolecule DNA


Deoxyribonuleic acid
It is made up of nucleotides (adenine,
guanine, cytosine, and thymine)
U.S. Department of Energy Human Genome Program,
http://www.ornl.gov/hgmis.
The parts of a nucleotide

1. nitrogenous base

2. deoxyribose sugar

3. phosphate group
U.S. Department of Energy Human Genome Program, http://w ww.ornl.gov/hgmis.
1
Where is DNA?
Focus on DNA…
DNA…
What is DNA?
DNA is a nucleic acid.
What does DNA do?
DNA contains the instructions for making
proteins.
What is DNA composed of?
Deoxyribose,, phosphate group, nitrogenous
Deoxyribose
base
Where is DNA located?
In the nucleus of each cell.
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
Chromosome: Tightly
wrapped DNA and
protein structure
found in our nucleus.
Gene: A segment of
DNA that determines
our traits.
What does DNA do?

Stores the information for making proteins
______ 1). Discovered the process
where genetic information form one
bacteria was transferred to another
(transformation).
______ 2). Determined genes were
made of DNA.
______ 3). Determined the shape of
DNA.
______ 4). Used radioactive isotopes to
prove DNA controlled traits.
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Who Discovered DNA?
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Friedrich Miecher
1869
Isolated DNA from the pus of surgical
bandages
Discovering DNA
(1)
•
•
Worked with the bacteria that cause pneumonia
Discovered transformation.
-- Transformation
Transformation:: Some molecule or group
of molecules control the function of organisms.
(2)
•
•
Transformation/Griffith
Griffith: (1928)
Avery: (1944)
Worked with bacteria
Determined genes were made of DNA
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Avery & Transformation
Discovering DNA—
DNA—cont.
(3)
•
•
•
Discovering DNA-cont.
Chargaff:
Chargaff: (1950)
Worked with the nucleotides of DNA samples
Discovered the amount of A = T ; C = G
(4)
•
Rosalind Franklin’
Franklin’s Picture of DNA
Franklin: (1951)
Worked with X-rays and DNA
Produced an X-ray image of DNA
Hershey and Chase
(5) Hershey and Chase: (1952)
Nucleic Acids

•Worked
with bacteriophages
-- Bacteriophage
Bacteriophage:: is a virus which
infects bacteria
•Proved genes were made of DNA not protein
Two types:

Deoxyribonucleic acids (DNA): contains the
instructions for making proteins.

(6) Watson and Crick: (1953)
•Worked
with Franklin’
Franklin’s X-rays of DNA to create
the double helix model of DNA
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Nucleic Acids

Large complex molecules made of nucleotide
monomers.
Nucleotides consist of three parts:
a. Five carbon sugar (pentose)
b. Phosphate group
c. Nitrogenous base
Figuring Out DNA Structure


The amino acids of proteins are specified by
unique sequences of nucleotides in DNA.
Ribonucleic acids (RNA): carries out the
instructions of DNA for making proteins
Who?
If you know the three parts that make up
a DNA molecule (phosphate group, ribose
sugar and a nitrogenous base), could you
figure it out?
Watson and Crick were able to determine
the structure of DNA by building on other
scientists’
scientists’ research.
3
DNA Components

A DNA molecule is made up of three
subunits:
Watson-Crick Model of DNA

A pentose sugar (deoxyribose
(deoxyribose))
Phosphate group
 Nitrogenous base
Between the strands:
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Nitrogenous bases of each strand are located very
close to each other along the center of the double
helix. Hydrogen bonds form between the following
pairs:
A-T
Adenine (A)
Guanine (G)
Cytosine (C)
 Thymine (T)

&
C-G

* these hydrogen bonds provide the force that
holds the two strands together.

life.nthu.edu.tw/~lslpc/ StrucBio/chapter7_1.html
Watson-Crick Model of DNA

The Strands:
2 strands
Composed of 5 carbon sugars and phosphate
groups (sugar-phosphate backbone)
 Double helix
 the sequence of nucleotides on one strand is
matched perfectly to the complementary
base sequence on the other strand.
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Nucleotide Pairings
If you know the pairings A-T & C-G and I give you a
single strand of DNA you should be able to figure out
the other strand.
1. The following is part of a gene contained on a single
strand of DNA. What is it’
it ’ s matching strand
(complementary strand)?:
A T T C A G C G T
T A A G T C G C A

2. RNA and DNA are both types of Nucleic Acids. What
are the 3 main differences between RNA and DNA?
life.nthu.edu.tw/~lslpc/ StrucBio/chapter7_1.html
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RNA and DNA Differences
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RNA
DNA
RNA: differs from DNA
- Contains a ribose sugar, not deoxyribose
- Has uracil (U) instead of thymine (T)
- Single stranded
What type of sugar is found in DNA
nucleotides?
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library.thinkquest.org/.../
library.thinkquest.org
/.../ R NA.htm
Journey into DNA
Interactive DNA Model
DNA Anatomy (animated DNA)
Structure of nucleic acids
library.thinkquest.org/. ../o verview.html
DNA Model Requirements
Due on Wednesday, 11/9
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Documentation:
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There must be a clear title identifying the model
A key must accompany the model, which identifies
every part of the model (each part of the nucleotide,
each nitrogenous base, and the hydrogen bond)
Identify a nucleotide, including the three parts to a
nucleotide
Identify the shape of your model
Model Construction:
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Large and neat
Creative use of color and materials
The model follows the key and there is correct base
pairing throughout the model
The model is able to form a double helix
(1) What will the mRNA code look like after
the following strand of DNA is transcribed
(changed into mRNA form)?
DNA: The big picture
DNA: The Big Picture
TACGCGATATCGAATATT
AU GCGCUAUAGCUUAUAA
The Central Idea:
Chromatin


When a cell is not
actively dividing, its
nucleus contains
chromatin,, a tangle of
chromatin
fibers composed of
protein and DNA.
Before cell division
chromatin organizes
itself into chromosomes
chromosomes..
Chromosome: Tightly
wrapped DNA and
protein structure found
in our nucleus

Chromatin

When the time
comes for the cell to
divide into two new
cells, all the DNA is
copied (replicated).
Why? DNA is
heritable. Each new
cell receives a
complete copy of all
the genetic material
in the "parent" cell.
http://www.animalgenome.org/edu/doe/fig4.gif
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One Gene
Gene One protein
How do genes code for proteins?
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Each DNA molecule
is made up of many
genes
gen
es-individual
-individual
segments of DNA
that contain the
instructions needed
to direct the
synthesis of a
specific protein with
a specific function.
Each gene codes for
ONE protein!
•
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Protein— A chain of
Protein—
subunits called amino
acids.
There are 20 amino acids.
The Genetic Code—
Code— The
sequence of nucleotides in
a gene determines the
sequence of amino acids in
a protein.
The sequence of amino
acids determines function
of the protein
RNA: Ribonucleic Acid
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Ultimately, it is our proteins
which determine our
characteristics!
DNA Quick Quiz
Gene on DNA strand:
TACATGCTAAAGTGCCATATT
Transcription
mRNA:
AUGUACGAUUUCACGGUAUAA
 Translation
Protein:
Met-Tyr-Asp-Phe-Thr-Val-stop
DNA CANNOT LEAVE THE NUCLEUS HOW
CAN IT MAKE PROTEINS? It doesn’
doesn’t make
them - it is the instructions.
RNA (Ribonucleic Acid): is the principle
molecule that carries out the instructions
coded in DNA,
DNA, primarily it makes proteins.
RNA differs from DNA in three main ways:
a) What are the 3 differences between DNA and RNA?
 RNA:
Contains a ribose sugar, not deoxyribose
Has uracil (U) instead of thymine (T)
Single stranded
b) Why is RNA necessary for the process of protein synthesis?
 DNA CANNOT LEAVE THE NUCLEUS! RNA carries the instructions
coded in DNA to the cytoplasm (ribosome) where protein synthesis
occurs.
2. In the Watson-Crick model of DNA, the two strands of the double helix are
joined together by what type of bond?
 Hydrogen bond
3. What is a gene?
gen
genes
es-individual
-individual segments of DNA that contain the instructions
needed to direct the synthesis of a specific protein with a specific
function.
DNA Replication
1.

DNA Replication
DNA Replication
What is DNA Replication?

The process of copying a cell’
cell’ s DNA.

To replicate = to copy
When would DNA need to be replicated?

Any time a cell divides to form new cells. Genetic
information must be passed to the new cells!
Why is DNA Replication described as “Semiconservative
Semiconservative”” ?

Semiconservative=
Semiconservative
=each new DNA molecule contains
one original strand and one new strand
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What are the steps in DNA
Replication?
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DNA Replication:
(1) DNA double helix unwinds
(2) Enzymes separate the 2 strands of
DNA by breaking the hydrogen bonds
(3) Free nucleotides link up to opposite
nucleotides of each DNA strand
(4) New hydrogen bonds form
(5) 2 new DNA strands wind into double
helix
Applying DNA Replication
Summary of DNA Replication:
Each parent double-stranded DNA molecule
is copied forming, two identical, doublestranded DNA molecules (daughter DNA
molecules)
Forms of RNA:
1). Messenger RNA (mRNA): Serves as a
messenger from DNA to the rest of the
cell and carries the instructions for the
assembly of amino acids into polypeptides.
2). Ribosomal RNA (rRNA
): Part of the
(rRNA):
ribosome where proteins are assembled.
3). Transfer RNA (tRNA
): Transfers
(tRNA):
Amino acids to the ribosome and helps
bind them.
Steps of Transcription
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RNA polymerase binds to DNA at the promoter (start)
site –unwinds and breaks the hydrogen bonds of the
DNA
RNA polymerase assembles free nucleotides into a
new mRNA chain, using complementary base pairing
As the new mRNA chain grows, RNA polymerase
moves along the DNA
The making of mRNA continues until the RNA
polymerase reaches the terminator (stop) site
RNA polymerase and new mRNA strand are released
Codons

Codon: The group of three nucleotides in mRNA that
Codon:
specifies an amino acid.
Each codes for a specific AA. There are 20 total AA.
Some codons are “synonymous
synonymous”” (coding for the same
AA).

There are 64 possible codons
codons,, shown on page 184
(when using the four possible nucleotides AUGC).

There are three stop signals which signify the end of a
genetic message on a mRNA strand.
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There is one codon that signals the start of the genetic
message on the mRNA strand.
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Slooze Worm Activity
The Language of mRNA:
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Only 4 letters:
mRNA: is made of AUCG and is read in
groups of three by the ribosome.
Example: AAACCCCAU (mRNA Strand)
If we break the strand into groups of
three what do we get?
AAA
CCC
CAU
The Genetic Code
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
UAA, UAG, UGA
AUG
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
What amino acid
would the codon
codon,,
AGA,, code for?
AGA
What amino acid
would the codon
codon,,
CAU,, code for?
CAU
UAA??
UAA
Genetic code:
 Proteins are made of polypeptides: polypeptides
are long chains of AA’
AA’s (there are 20 different
amino acids).
 The order of amino acids determines the
properties of the protein.
 DNA is the instructions for making proteins.
Genetic disorders may be a result in poor
instructions (DNA). If the instructions are
wrong the protein will not work.
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Steps of Translation
(1) Ribosome binds to mRNA at the start codon
codon,,
AUG
(2) tRNA delivers amino acid (AA)
(3) tRNA continues to deliver the proper AA’
AA’ s as
the ribosome moves along the mRNA
(4) The ribosomes assemble the AA’
AA’s into a
polypeptide chain (protein)
(5) Translation finishes when a stop codon is
reached. The ribosome and protein are released
Figuring Out DNA Structure


If you know the three parts that make up
a DNA molecule (phosphate group, ribose
sugar and a nitrogenous base), could you
figure it out?
The Major Players of Translation
•
•
•
•
Ribosome
mRNA--codon
mRNA--codon
tRNA-tRNA-Amino acids
Watson and Crick were able to determine
the structure of DNA by building on other
scientists’
scientists’ research.
RNA Problem


The following strand of mRNA came from the transcription of DNA.
Using the strand of RNA, break it into codons and determine the
protein that will be formed.
Nucleic Actual
Acid
Name
mRNA
AUAUUUAAACCAGGCGAGAUUCCCUAUGGGGUACGU
AUA or AUU = I
AAA or GGG or CCC = O
GGC = E
UUU or UAU = L
CCA = V
GAG = B
GUA = G
CGU = Y
Shape Location Function
in Cell
During Protein
Synthesis
1. The following section of DNA is the gene that caused the bacteria colonies
to fluoresce (glow) in the transformation experiment:
TACATGCGTACCGGGCATTATATT
a) Transcribe the above strand of DNA into Messenger RNA (mRNA).
DNA
AUGUACGCAUGGCCCGUAAUAUAA

mRNA
tRNA
Test Review:
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c) What amino acids will this mRNA code
for?
AUG UAC GCA UGG CCC GUA AUA UAA
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Methionine (start)
(start)—
—Tyrosine
Tyrosine—
— Alanine
Alanine—
—Tryptophan-Proline—
Proline
—Valine--Isoleucine--stop
How many codons are in the above mRNA?
AUG UAC GCA UGG CCC GUA AUA UAA
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Define the following terms:
Nucleotide:
T hree parts of a nucleotide: How they pair up, where they bond together and the type of bond
that joins
them:
T ransformation:
Griffith:
A very:
Hershey-Chase:
W atson-Crick:
DNA replication:
List Three differences between DNA & RNA
T ranscription:
T hree types of RNA:
Genetic Code:
Codons::
Codons
T ranslation:
How do we produce proteins and why are these proteins important:
W hat is a Polypeptide:
How many AA’
AA ’ s are there:
How can DNA code for the production of our traits if there are only four different nucleotides:
If given a strand of DNA you should be able to:
- Identify the other strand of DNA
- Determine the mRNA
- Determine the amino acids the mRNA will code for
Problem: If you are given the following strand of DNA what is the other strand? What will the mRNA look
like after transcription of the given strand? What amino acids will the mRNA code for and where does
transcription and translation take place? What is the start codon and what is the stop codon
codon??
DNA strand:
T ACCCCGGCTTTACT
Genes

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One gene one protein
genes specify/code for the proteins that make
up an organism and give it it’
it’s traits.
What are genes made of?
- segments of DNA that code for a specific trait.



What are chromosomes?
- compacted DNA (storage)
Genetic disorders are a result of improper
proteins.
DNA-
DNA RNARNA-
 Protein
Protein
 gives us a trait
8
Genes
Disease and Genetic Counseling
What is Huntington’
Huntington’s Disease? How is it
transmitted? What are the symptoms?
Treatment options?
 What are the roles of genetic counselors?
 What do you think about the idea genetic
counseling? What are the potential
positive things that may result from this
process? What are the potential negative
results?

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How do genes actually determine the
traits of an organism?
Genes specify/code for the proteins that
make up an organism and give it it’
it’s traits.
What are genes made of?
Gel Electro



Gel Electro
Why do Flies Glow
Paternity test
- segments of DNA that code for a specific trait.

What are chromosomes?
- compacted DNA (storage)
Translation: nucleotides in mRNA are decoded into a
sequence of amino acids forming a polypeptide. This
occurs in the cytoplasm of the cell.
In a nutshell:
- RNA polymerase transcribes DNA, making mRNA (it
moves out of the nucleus)
- In the cytoplasm of the cell: Ribosome’
Ribosome’s read the
codons in mRNA (the message is decoded).
- tRNA molecules take the proper AA’
AA’s to the ribosomes
ribosomes..
- The ribosomes assemble the AA’
AA’s into a
proteins/polypeptide.
mRNA, tRNA
tRNA,, rRNA
rRNA:: Are sections of RNA transcribed
from DNA.
* there is usually more than one ribosome translating
mRNA at a time. Why?
9
Human Genome Project (1990-2003)
http://www.ornl.gov/sci/techresources/Human_Genome/home.shtml
http://
www.ornl.gov/sci/techresources/Human_Genome/home.shtml
Project Goals:
 identify all genes in human DNA,
 determine the sequences of the chemical base
pairs that make up human DNA,
Project Results:
• Human DNA is made up of approximately
25,000-33,000 protein-coding genes
• This equates to 3 billion chemical base pairs
• Surprised? The simple roundworm C. elegans
has about 20,000 genes!
10