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Chapter 5: DNA, Gene
Expression, and Biotechnology
What is the genetic 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.
 Discuss biotechnology in agriculture.
 Describe biotechnology and its implications
for human health.

5.1–5.5
DNA: what is it, and
what does it do?
5.1 “The DNA 200”
Knowledge about DNA is
increasing justice in the world.
Take-home message 5.1
 DNA
is a molecule that all living organisms
carry in every cell in their body.
Take-home message 5.1
 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.
5.2 The DNA molecule contains
instructions for the development
and functioning of all living
organisms.
DNA “Double Helix”
Nucleic acids and nucleotides
Sugars, Phosphates,
and Bases
A, T, C, and G
Base pairs
Which component of a DNA
macromolecule will dictate
instructions to the cell?
1.
2.
3.
4.
The order of sugars (ribose) in the DNA.
The order of phosphates in the DNA.
The order of bases (A,G,T,C) in a DNA.
All of the above
Which answer below will base
pair with the DNA sequence
below?
TATTAGTAGGTTA
1. ATAATCATCCAAT
2. AUAAUCAUCCAAU
3. ATTGGATGATTAT
4. TATTAGTAGGTTA
Take-home message 5.2
 DNA
is a nucleic acid, a macromolecule
that stores information.
 It
consists of individual units called
nucleotides: a sugar, a phosphate group,
and a nitrogen-containing base.
Take-home message 5.2
 DNA’s
structure resembles a twisted
ladder, with the sugar and phosphate
groups serving as the backbones of the
molecule and base pairs serving as the
rungs.
5.3 Genes are sections of DNA that
contain instructions for making
proteins.
Why is DNA considered the
universal code for all life on
earth?
Genes
A
sequence of bases in a DNA molecule
that carries the information necessary for
producing a functional product, usually a
protein molecule or RNA
Take-home message 5.3
 DNA
is a universal language that provides
the instructions for building all the
structures of all living organisms.
 The
full set of DNA an organism carries is
called its genome.
Take-home message 5.3
 In
prokaryotes, the DNA occurs in circular
pieces.
 In
eukaryotes, the genome is divided
among smaller, linear strands of DNA
called chromosomes.
Take-home message 5.3
A
gene is a sequence of bases in a DNA
molecule that carries the information
necessary for producing a functional
product, usually a protein molecule or
RNA.
5.4 Not all DNA contains instructions
for making proteins.
Insert figure 5-8
An onion has five times as
much DNA as a human.
Why doesn’t that make them
more complex than us?
The proportion
of the DNA
that codes for
genes
Introns
 Non-coding
regions of DNA
 May
take the form of short (or long)
sequences that are repeated thousands of
times
 May
also consist of gene fragments,
duplicate versions of genes, and
pseudogenes
Take-home message 5.4
 Only
a small fraction of the DNA in
eukaryotic species codes for genes.
• The function of the rest is still a mystery,
although it may play a role in gene
regulation.
5.5 How do genes work?
An overview

Genotype
• all of the genes contained in an
organism

Phenotype
• the physical manifestations of the
instructions
Take-home message 5.5
 The
genes in strands of DNA are a
storehouse of information, an instruction
book.
Take-home message 5.5
The process by which this information is
used to build an organism occurs in two
main steps:
 transcription,
in which a copy of the gene’s
base sequence is made, and
 translation,
in which that copy is used to
direct the production of a protein.
5.6–5.8
Building organisms:
information in DNA
directs the production
of the molecules that
make up an organism.
5.6 Transcription: Reading the
information coded in DNA
Which answer below represents the
mRNA strand copied from the DNA
strand below?
TATTAGTAGGTTA
1. UAUUACUACCUUA
2. AUAAUCAUCCAAU
3. ATTGGATGATTAT
4. ATAATCATCCAAT
Take-home message 5.6
 Transcription
is the first step in the two-step
process by which DNA directs the synthesis
of proteins.
 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 In translation, the mRNA
copy of the information from
DNA is used to build functional
molecules.
Several ingredients must be present in the
cytoplasm for translation to occur.
 Free
amino acids
 Ribosomal
 Transfer
units
RNA
The Genetic Code
Insert figure 5-14
Insert figure 5-15
Translate the following mRNA
sequence using the codon table
from your book.
AGGGAUGGCGAAACAACCA
1. Arginine-aspartate-glycine-glutamate-threonine threonine
2. Methionine-alanine-lysine-glutamine-proline
3. Threonine-asparigine-lysine-alanine-valine-glycine
4. Methionine-alanine-lysine-histidine-proline
Take-home message 5.7
 Translation
is the second step in the twostep process by which DNA directs the
synthesis of proteins.
 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.
5.11–5.13
Biotechnology is
producing
improvements in
agriculture.
Insert section 5.11-5.13 opener photo
5.11 What is biotechnology?
Genetic Engineering
 Adding,
deleting, or transplanting genes
from one organism to another, to alter the
organisms in useful ways
Insert figure 5-24
Insert figure 5-25
Insert figure 5-26
Insert figure 5-27
Insert figure 5-28
Insert figure 5-29
Which DNA probe below could be used
for isolating bacteria that carry the
following gene from a gene library?
TTGACGTATTGCCTTGGAAGCGTA
1.
2.
3.
4.
TGCCTT
ATGCGA
ACTGCA
TGACGT
Take-home message 5.11
 Biotechnology
is the use of technology to
modify organisms, cells, and their
molecules to achieve practical benefits.
Take-home message 5.11
 Modern
molecular methods make it
possible to cut and copy DNA from one
organism and deliver it to another.
Take-home message 5.11
 The
methods rely on naturally occurring
restriction enzymes for cutting DNA, the
polymerase chain reaction for amplifying
small amounts of DNA, inserting the DNA
into bacterial or viral vectors, and cloning
and identifying the cells with the
transferred DNA of interest.
5.12
Biotechnology
can improve food
nutrition and
make farming
more efficient
and eco-friendly.
Insert figure 5-30
How might a genetically
modified plant help 500
million malnourished people?
Nutrient-rich “golden rice”
Almost everyone in the United States
consumes genetically modified foods
regularly without knowing it.
What foods are responsible for this?
Is there more genetically modified
corn or genetically modified cotton
produced in the United States?
1.
2.
3.
4.
There is more genetically
modified cotton grown in the
United States.
There is more genetically
modified corn grown in the
United States.
I don’t know the absolute
amount of corn and cotton grown
in the United States.
I don’t know because it is not
clear how they calculated the
percentages in the graph.
Insect Resistance
Insert figure 5-33
How can genetically modified
plants lead to reduced pesticide
use by farmers?
Herbicide Resistance
Faster Growth and Bigger Bodies
When making Bt corn, the scientists
inserted the Bt gene from ________
into the corn plant’s _______.
1.
2.
3.
4.
carrots……cells
bacteria….genome
carrots…..genome
bacteria….cells
Take-home message 5.12
 Biotechnology
has led to important
improvements in agriculture by using
transgenic plants and animals to produce
more nutritious food.
Take-home message 5.12
 Even
more significant is the extent to
which biotechnology has reduced the
environmental and financial costs of
producing food
 through
the creation of herbicide-resistant
and insect-resistant crops
Take-home message 5.12
 The
ecological and health risks of such
widespread use of transgenic species are
not fully understood and are potentially
great.
5.13 Fears and risks: Are
genetically modified foods safe?
Fear #1: Organisms that we want to kill may
become invincible.
 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
dangerous.
 Fear #5: Loss of genetic diversity among crop
plants is risky.
 Fear #6: Hidden costs may reduce the financial
advantages of genetically modified crops.

We should continue to develop
genetically modified organisms.
1.
2.
3.
4.
5.
Strongly agree
Agree
Neutral
Disagree
Strongly disagree
Take-home message 5.13
 More
and more genetically modified foods
are being created using modern methods
of recombinant DNA technology.
 Some
legitimate fears among the public
remain, however, about the safety of
these foods given that their development
relies on such new technology and about
the long-term financial advantages they
offer.
5.14–5.17
Biotechnology
has the potential
for improving
human health (and
criminal justice)
5.14 The treatment of diseases and
production of medicines are improved
with biotechnology
 Prevent
 Cure
diseases
diseases
 Treating
diseases
• The treatment of diabetes
Insert figure 5-39
Why do some bacteria
produce human insulin?
Recombinant DNA technology
Take-home message 5.14
 Biotechnology
has led to some notable
successes in treating diseases, usually by
producing medicines more efficiently and
more effectively than they can be
produced with traditional methods.
5.16 Cloning—ranging
from genes to organs
to individuals—offers
both promise and
perils
Are there any medical justifications
for cloning?
We should pursue cloning in animals
but not humans.
1.
2.
3.
4.
5.
Strongly agree
Agree
Neutral
Disagree
Strongly disagree
We should pursue cloning in humans
for the purpose of developing or
performing medical treatments.
1.
2.
3.
4.
5.
Strongly agree
Agree
Neutral
Disagree
Strongly disagree
Take-home message 5.16
 Cloning
of individuals has potential
benefits in agriculture and medicine, but
ethical questions linger.
5.17 DNA as an individual identifier: the
uses and abuses of DNA fingerprinting
Insert figure 5-45c
Insert figure 5-46
DNA samples were collected from a crime scene
and from three suspects. DNA fragments were
analyzed using electrophoresis. Using the DNA
fingerprint information below, determine which
suspect was present at the crime scene.
Crime
Scene
1.
2.
3.
4.
Suspect #1
Suspect #2
Suspect #3
All of the above.
Suspect
#1
Suspect Suspect
#2
#3
What is a DNA
fingerprint?
Take-home message 5.17
 Comparisons
of highly variable DNA
regions have forensic value in identifying
tissue specimens and determining the
individual from whom they came.