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Chapter 5: DNA, Gene
Expression, and Biotechnology
What is the code and how is it harnessed?
Lectures by Mark Manteuffel, St. Louis Community College
Learning Objectives
Describe what DNA is and what it does.
 Explain the process of gene expression and
the collaboration of nature and nurture.
 Explain the causes and effects of damage to
the genetic code.
 Describe biotechnology and its implications
for human health.
 Discuss biotechnology today and tomorrow.
 Discuss biotechnology in agriculture.

5.1 “The DNA 200”
Knowledge about DNA is
increasing justice in the world.
What is the
most common
reason why
DNA analyses
overturn
incorrect
criminal
convictions?
Take-home message 5.1
 DNA
is a molecule that all living organisms
carry in every cell in their body.
 Unique in virtually every person, DNA can
serve as an individual identifier, left behind
us as we go about our lives.
 This is a fact that is used increasingly to
ensure greater justice in our society, such
as through establishing the innocence of
individuals wrongly convicted of crimes.
Two Important Features of DNA
(1) DNA contains the
instructions on how to
create a body and
control its growth and
development.
(2) The instructions
encoded in the DNA
molecule are passed
down from parent to
offspring.
Rosalind Franklin
DNA “Double Helix” – a nucleic acid
DNA
consists of
individual
units called
nucleotides:
a sugar, a
phosphate
group, and a
nitrogencontaining
base.
How does knowing the structure of
DNA help us?
• Manipulating DNA
allows us to
manipulate
genetic traits
(proteins) and
treat genetic
disorders (gene
therapy).
• HIV treatment
• Biomimicry
Helix Wind Turbine – quieter,
smaller, less impact on birds and
bats – residential scale.
AZT mimics the chemical
shape of Thymine, and when
HIV viral DNA tries to replicate,
AZT attaches to block.
• The genetic code is
shared by all
organisms.
• This tobacco plant
is expressing a
firefly gene.
• The gene codes for
the firefly enzyme
(a protein) that
causes it to glow.
The number of chromosomes varies from
species to species.

Corn has 10 unique chromosomes.

Fruit flies have only 4.

Dogs have 39 chromosomes.

Goldfish have 47 chromosomes.

Humans have 46 chromosomes.

Individuals in each of these species inherit one
copy of each chromosome from each parent.
5.3 Genes are
sections of DNA
that contain
instructions for
making proteins.
DNA is a universal
language that
provides the
instructions for
building all the
structures of all living
organisms.
Alleles are
alternate
versions of a
gene that
code for a the
same trait.
Usually they
occur in pairs
as dominant
and recessive
alleles.
5.4 Not all DNA contains instructions
for making proteins.
Why doesn’t
that make an
amoeba more
complex than
a human?
The Proportion of
the DNA
That Codes for
Genes:
Just because we
don’t yet know it’s
function doesn’t
mean non-coding
DNA has no
function.
Introns = Noncoding regions of
DNA
May take the
form of short (or
long) sequences
that are repeated
thousands of
times, may also
consist of gene
fragments or
duplicate
versions of
genes.
FROM EGG TO ORGANISM:
HOW AND WHY GENES ARE REGULATED
• Four of the
many different
types of
human cells
– They all share
the same
genome
– What makes
them different?
(a) Three muscle cells (partial)
(b) A nerve cell (partial)
(c) Sperm cells
(d) Blood cells
The flow of
information
from genes to
proteins
(genotype to
phenotype) is
called gene
expression. In
the mature
organisms, each
cell type has a
different pattern
of turned-on
genes.
Genotype = all of the genes contained in an
organism
Phenotype = the physical manifestations of
the instructions
5.6 Transcription: reading the
information coded in DNA
In transcription, a single copy of one specific
gene within the DNA is made, in the form of a
molecule of mRNA, which moves where it can
be translated into a protein.
5.7 Translation: using information
from DNA to build usable molecules
In translation, the information from a gene that
has been carried by the nucleotide sequence
of an mRNA is read, and ingredients present
in the cell’s cytoplasm are used to produce a
protein.
Several ingredients must be present in the
cytoplasm for translation to occur.

Transfer RNA

Free amino acids

Ribosomal units
The amino acids
of a polypeptide
correspond with
the nucleotides
of a mRNA
molecule.
This is how
translation
occurs.
Amino acids are organized by triplets called codons.
Overview:
– Transcription
occurs in the
nucleus.
– Translation
occurs in the
cytoplasm.
• A mutation
– Any change in the nucleotide sequence of DNA
can have a wide range of effects.
Mutant hemoglobin DNA
mRNA
mRNA
Normal hemoglobin
Glu
Sickle-cell hemoglobin
Val
Figure 10.21
Breast Cancer in Humans
 Two
human genes, called BRCA1 and
BRCA2
 More
than 200 different changes in the
DNA sequences of these genes have been
detected, each of which results in an
increased risk of developing breast cancer.
Types of Mutations
– Can be divided
into two general
categories
• Base substitution
• Nucleotide
deletion or
insertion
– Can result in
positive, negative,
or nonfunctional
changes in
proteins.
Met
Lys
Phe
Gly
Ala
Met
Lys
Phe
Ser
Ala
Figure 10.22a
Mutations plan an important role in evolution.
Take-home message 5.9
 Most
genetic diseases result from
individual mutations that cause a gene to
produce a non-functioning enzyme, which
in turn blocks the functioning of a
metabolic pathway.
A “fastflush”
response
• Mutations may result from
– Errors in DNA replication
(spontaneous mutations)
– Physical or chemical agents
(mutagens)
VIRUSES: GENES IN PACKAGES
• Viruses sit on the fence between life and nonlife.
– They exhibit
some but not
all
characteristics
of living
organisms
– They cannot
reproduce
outside of a
host cell.
Figure 10.24
A virus uses the host cell’s “machinery” to transcribe and
translate its own DNA or RNA; it takes over the host cell,
multiplies, bursts, and releases new viral particles into the
host organism.
5.10 What is biotechnology?
Genetic Engineering
 Adding,
deleting, or transplanting genes
from one organism to another, to alter the
organisms in useful ways
 This creates recombinant organisms or
genetically modified organisms.
How is Genetic Engineering different
from Artificial Selection?
• Natural Selection
– Requires environmental pressures, genetic
variability, and successful reproduction.
• Artificial Selection
– breeding plants and animals for desired traits
• Genetic Modification/Engineering
– Creating new genetic combinations
(recombinant organisms) in the lab
– Crossing kingdom (and species) boundaries
Overview: Cut
out the gene of
interest, paste it
into a bacterial
plasmid, and test
the colony for
gene expression.
Step 1: Use
Restriction
Enzymes to
recognize a
specific sequence
and cut out the
gene of interest.
Different enzymes
are used to cut at
different
sequences.
Step 2: Use PCR to
amplify or clone the
gene of interest.
The DNA polymerase
enzyme is used
instead of the RNA
polymerase because
we’re making more
DNA instead of
transcribing mRNA,
but the process is
similar.
Step 3: Paste the gene
of interest into bacteria
DNA (a circular
plasmid). Incorporate
the plasmid into the
bacteria cell using a
gene gun, a viral
promoter, or electrical
shock.
The DNA ligase
enzyme pastes the
ends together.
Cell containing gene
of interest
Host cell
1
DNA
Recombinant DNA
(host DNA plus
gene of interest)
2
Gene of
interest
Cell multiplies and
produces protein
3
Genes may be inserted
into another organism
Protein may be harvested
OR
Gene for pest resistance
inserted into plants
Protein dissolves blood clots
in heart attack therapy
Biotech advances in human health fall into
three categories:
(1) producing
medicines to
treat diseases
(2) curing disease
(3) preventing
diseases from
occurring in
the first place.
By transferring
the gene for a
desired protein
product into a
bacterium,
proteins can
be produced in
large
quantities.
Curing diseases with
biotechnology
Using Stem Cells
and Gene therapy
and the correction
of malfunctioning
genes
Stem Cells: Embryonic and Adult
• Embryonic stem cells are undifferentiated cells in
the early animal embryo that give rise to
specialized cells. Grown in the laboratory, certain
growth factors can induce changes in gene
expression so that the cells may develop into a
certain cell type.
• Adult stem cells are partially differentiated cells
present in adult tissues in order to generate
replacements for specialized cells and tissues.
– More difficult to grow in laboratory culture
– Can be harvested from adult patients avoiding the
controversy surrounding the embryo and with less risk
of immune system rejection.
Therapeutic Cloning and Stem Cells
HUMAN GENE
THERAPY
• Human gene therapy
is a recombinant
DNA procedure that
seeks to treat
disease by replacing
the mutant version
with a properly
functioning one.
Why has gene therapy had
such a poor record of success
in curing diseases?
(1) Difficulty getting the working gene into the
specific cells where it is needed.
(2) Difficulty getting the working gene into enough
cells and at the right rate to have a physiological
effect.
(3) Problems with the transfer organism getting into
unintended cells (virus side effects)
Is a given set of parents likely to
produce a baby with a genetic
disease?
Prevention
has to do with
screening
parents,
developing
fetuses,
growing
children, and
adults
Ethical Dilemmas
 Discrimination
 Genetic
2008
 Health
Information Nondiscrimination Act of
insurance
 Does
not cover life, disability or long-term
care insurance
 How
to proceed with the information?
 Should
the parents terminate the pregnancy?
5.17 DNA as an individual identifier: the
uses and abuses of DNA fingerprinting
What is a DNA
fingerprint?
• The goal of DNA
fingerprinting by is
to determine
whether or not
samples of DNA
contain identical
genetic markers.
Genetic markers
are unique unless
you have an
identical twin.
Crime scene
1
DNA collected
2
DNA amplified if necessary
3
DNA cut into fragments
4
DNA fragments
compared
Suspect 1
Suspect 2
Figure 12.13
Crime scene
DNA
Suspect DNA
Fragment w
Cut
Fragment z
Fragment x
Cut
Fragment y
Cut
Fragment y
Figure 12.16
– Gel electrophoresis is a method for sorting
these fragments based on their length and
electrical charge.
Mixture of DNA
fragments of
different sizes
Longer
(slower)
fragments
Power
source
Gel
Shorter
(faster)
fragments
Completed gel
Figure 12.17
• The DNA fragments are visualized as
“bands” on the gel
– The bands of different DNA samples can then
be compared.
Crime
scene
DNA
Suspect
DNA
Longer
fragments
Shorter
fragments
Figure 12.18
• DNA
fingerprints
from a murder
case
• Guilty or
innocent?
• This blood on
the defendant’s
clothes
matches the
victim.
Blood on defendant’s
clothes
Defendant’s
blood
Victim’s
blood
5.18 DNA sequences reveal
evolutionary relatedness
(1) Mapping Genetic Landscapes:
The Human Genome Project
(2) Building Earth’s Family Tree
When we say humans and
chimps are genetically 96%
identical, what do we mean?
An indication that chimps are our closest living
relative.
Remember most of that DNA doesn’t code for
functional proteins.
When comparing only the coding parts of the
genome, we find only 29% of our genes code for
the same exact proteins found in chimps.
5.19 The promise and
perils of cloning
From organs (therapeutic cloning)
to individuals (reproductive or
whole organism cloning)
• Differentiated plant cells
– Have the ability to develop into a whole
new organism (produce plant clones
– reproductive cloning)
Root of
carrot plant
Plantlet
Cell division
in culture
Single cell
Root cells in
growth medium
Adult plant
Reproductive Cloning of Animals
– Involves replacing nuclei of egg cells with nuclei
from differentiated cells
– Has been used to clone a variety of animals
FDA has approved cloned animals for meat and milk.
Dolly, March
1997
March, 2002
Nov., 2001
May, 2003
Health problems are associated with
cloned species. These little guys did
not live a full natural life.
ANDi,
Rhesus
monkey
GM’d to
carry a
fluorescent
protein
from a
jellyfish
Jan., 2001
Is it possible to
clone a
dinosaur? If so,
how could it be
done?
5.14 Producing
more nutritious
and better food
with
biotechnology
How might a
genetically
modified
plant help
500 million
malnourished
people?
Nutrientrich
“golden
rice”
Putting vaccines in potatoes…
How can genetically modified plants lead to
reduced pesticide use by farmers?
But what about the pesticides in our diet?
Herbicide Resistance
Are plants
like LibertyLink Corn
and Roundup Ready
Soy good for
the
ecosystem?
Farmers still
pay the
costs.
Faster Growth and Bigger Bodies
Do we want more growth hormones in our diet?
What happens if these giant fish escape?
Almost everyone in the U.S. consumes
genetically modified foods regularly
without knowing it.
Do we have a choice?
Fears and
risks: the
safety of
genetically
modified
foods?



Fear #1. Organisms that we want to kill may
become invincible. How long before the pests
evolve to become resistant to the pesticide
gene in plants?
Fear #2. Organisms that we don’t want to kill
may be killed inadvertently.
Fear #3. Genetically modified crops are not
tested or regulated adequately.







Fear #4. Eating genetically modified foods is potentially
dangerous. The long-term effects are unknown. Allergies
may develop.
Fear #5. Have we lost consumer freedom? If GM crops are
not labeled and there is a health problem, it will be very
hard to prove accountability.
Fear #6. Loss of genetic diversity among crop plants is risky.
Fear #7. Hidden costs may reduce the financial advantages
of genetically modified crops.
Fear #8. These combinations “matings” could never occur in
nature.
Fear #9. Recombinant DNA technology could create
hazardous new pathogens (i.e. if cancer cell genes were
transferred into an infectious bacteria or virus).
Is it even ethical to patent living organisms?