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Gene Expression and Genetic
Technologies
Differentiation
• Cells become specialized in process and function
by turning different genes off and on.
• All cells (in an organism) have the same genetic
information
– Except sex cells
• When cells differentiate during development,
some genes are turned off while others are
turned on
– This is determined with “master control genes”
– Act like conductors, directing the cell to become
specific cell types
Repressor and
Promotor
• Genes are turned off
and on based on their
promoters
• Repressor: genes are
turned off by a
repressor binding to
their promoter, which
blocks transcription
• Promoter: section of a
gene that identifies
location of a gene
Differentiation
• This is the process
followed by stem cells
– Stem Cells:
Undifferentiated cells
that can differentiate
into any other cell type
– This is how stem cell
therapies could heal
disease
• Stem cells would treat
damaged tissues by
replacing the damaged
cells
Genes & Environment
• While some genes are
controlled by master
genes, other genes are
turned off an on based on
the cells environment
• Environmental Factors
That can influence Genes:
– Resource availability
– Predators
– Abiotic Factors
Norm of Reaction
Vestigial wings in Drosophila
Curve illustrating different wing sizes in fruit flies based in temperature during development.
Environmental Effects on Gene Expression
• Himalayan markings: temperature sensitive allele
• Fur is usually white
– When grown in cold temperatures, fur exhibits black phenotype
Environmental Effects on gene
expression
• Some flowers
– Sensitive to changes in pH
Ch. 13 Genetic Technologies
What You’ll Learn
• You will evaluate the importance of plant and
animal breeding to humans
You will summarize the steps used to engineer
transgenic organisms.
You will analyze how mapping the human
genome is benefitting human life.
We have been manipulating DNA for
generations!
• Artificial breeding
– creating new breeds of animals & new crop
plants to improve our food
Selective Breeding
• From ancient times, breeders have chosen plants and animals
with the most desired traits to serve as parents of the next
generation.
• Breeders of plants and animals want to be sure that their
populations breed consistently so that each member shows the
desired trait.
• selective breeding requires time, patience, and several
generations of offspring before the desired trait becomes
common in a population.
• Increasing the frequency of desired alleles in a population is the
essence of genetic technology.
Inbreeding develops pure lines
• Inbreeding is mating between
closely related individuals. It
results in offspring that are
homozygous for most traits.
• To make sure that breeds
consistently exhibit a trait and to
eliminate any undesired traits
• can bring out harmful, recessive
traits because there is a greater
chance that two closely related
individuals both may carry a
harmful recessive allele for the
trait.
•Horses and dogs are two
examples of animals that
breeders have developed as
pure breeds.
Hybrids are usually bigger and better
• hybrid is the offspring
of parents that have
different forms of a
trait.
• produced by crossing
two purebred plants
are often larger and
stronger than their
parents.
Test crosses can determine genotypes
• organisms that are either homozygous dominant
or heterozygous for a trait controlled by
Mendelian inheritance have the same phenotype.
• One way to determine the genotype of an
organism is to perform a test cross.
• A test cross is a cross of an individual of unknown
genotype with an individual of known genotype.
• The pattern of observed phenotypes in the
offspring can help determine the unknown
genotype of the parent.
• Section Objectives:
• Summarize the steps used to engineer transgenic
organisms.
• Give examples of applications and benefits of genetic
engineering.
Genetic Engineering
• Genetic engineering is a faster and more reliable method
for increasing the frequency of a specific allele in a
population
• This method involves cutting—or cleaving—DNA from
one organism into small fragments and inserting the
fragments into a host organism of the same or a
different species.
• You also may hear genetic engineering referred to as
recombinant DNA technology
• Recombinant DNA is made by connecting or
recombining, fragments of DNA from different sources.
Can we mix genes from one creature to
another?
YES!
How is this possible??
• Remember: The code is
universal!!
• Since all living organisms…
– use the same DNA
– use the same code book
– read their genes the same
way
• Genes can be moved
from one organism to
another.
Mixing genes for medicine…
• Allowing organisms to produce new proteins
– bacteria producing human insulin
– bacteria producing human growth hormone
Recombinant DNA
Enzymes are used to “cut and paste”
• Steps involved:
• Isolate a desired gene using:
restriction enzymes: are bacterial proteins that have the
ability to cut both strands of the DNA molecule at a specific
nucleotide sequence. (the scissors doing the cut
• DNA ligase “pastes” the DNA fragments
together (the glue)
• The result is recombinant DNA
How do we do mix genes?
• Steps in Genetic engineering
1. Locate the desired gene
2. cut the DNA in both organisms
3. paste gene from one creature into other creature’s
DNA
4. insert new chromosome into organism
5. organism copies new gene as if it were its own
6. organism reads gene as if it were its own
7. organism produces NEW protein:
Remember: we all use the same genetic code!
Cutting DNA
• DNA “scissors”
– Restriction enzymes that cut DNA
• used by bacteria to cut up DNA of
attacking viruses
• EcoRI, HindIII, BamHI
– cut DNA at specific sites
• enzymes look for specific base sequences
GTAACG|AATTCACGCTT
GTAACGAATTCACGCTT
CATTGCTTAA|GTGCGAA
CATTGCTTAAGTGCGAA
Restriction enzymes
• Cut DNA at specific sites
– leave “sticky ends”
restriction enzyme cut site
GTAACGAATTCACGCTT
CATTGCTTAAGTGCGAA
restriction enzyme cut site
GTAACG AATTCACGCTT
CATTGCTTAA GTGCGAA
Sticky ends
• Cut other DNA with same enzymes
– leave “sticky ends” on both
– can glue DNA together at “sticky ends”
GTAACG AATTCACGCTT
CATTGCTTAA GTGCGAA
gene
you want
GGACCTG AATTCCGGATA
CCTGGACTTAA GGCCTAT
chromosome
want to add
gene to
GGACCTG AATTCACGCTT
CCTGGACTTAA GTGCGAA
combined
DNA
Sticky ends help glue genes together
cut sites
gene you want
cut sites
TTGTAACGAATTCTACGAATGGTTACATCGCCGAATTCACGCTT
AACATTGCTTAAGATGCTTACCAATGTAGCGGCTTAAGTGCGAA
AATTCTACGAATGGTTACATCGCCG
GATGCTTACCAATGTAGCGGCTTAA
sticky ends
cut sites
isolated gene
chromosome want to add gene to
AATGGTTACTTGTAACG AATTCTACGATCGCCGATTCAACGCTT
TTACCAATGAACATTGCTTAA GATGCTAGCGGCTAAGTTGCGAA
DNA ligase joins the strands
sticky ends stick together
Recombinant DNA molecule
chromosome with new gene added
TAACGAATTCTACGAATGGTTACATCGCCGAATTCTACGATC
CATTGCTTAAGATGCTTACCAATGTAGCGGCTTAAGATGCTAGC
Why mix genes together?
• Gene produces protein in different
organism or different individual
human insulin gene in bacteria
TAACGAATTCTACGAATGGTTACATCGCCGAATTCTACGATC
CATTGCTTAAGATGCTTACCAATGTAGCGGCTTAAGATGCTAGC
“new” protein from organism
ex: human insulin from bacteria
aa aa aa aa aa aa aa aa aa aa
bacteria
human insulin
Uses of genetic engineering
• Genetically modified organisms (GMO)
– enabling plants to produce new proteins
• Protect crops from insects: BT corn
– corn produces a bacterial toxin that kills corn borer
(caterpillar pest of corn)
• Extend growing season: fishberries
– strawberries with an anti-freezing gene from flounder
• Improve quality of food: golden rice
– rice producing vitamin A
improves nutritional value
Vectors transfer DNA
• Vector is the means by
which DNA from another
species can be carried into
the host cell.
• may be biological or
mechanical.
• Biological vectors include
viruses and plasmids.
– A plasmid, is a small ring of
DNA found in a bacterial cell.
• Mechanical vectors include
a micropipette
Plasmids
Bacteria
• Bacteria are great!
– one-celled organisms
– reproduce by mitosis
• easy to grow, fast to grow
– generation every ~20 minutes
There’s more…
• Plasmids
– small extra circles of DNA
– carry extra genes that bacteria can use
– can be swapped between bacteria
• rapid evolution = antibiotic resistance
– can be picked up
from environment
How can plasmids help us?
• A way to get genes into bacteria easily
– insert new gene into plasmid
– insert plasmid into bacteria = vector
– bacteria now expresses new gene
• bacteria make new protein
gene from
other organism
cut DNA
plasmid
recombinant
plasmid
+
vector
glue DNA
transformed
bacteria
Grow bacteria…make more
gene from
other organism
recombinant
plasmid
+
vector
plasmid
grow
bacteria
harvest (purify)
protein
transformed
bacteria
1..Isolate DNA
from two sources
Gene cloning
• Bacteria take the recombinant
plasmids and reproduce
• This clones the plasmids and
the genes they carry
• Clones are genetically
identical copies.
– Products of the gene can
then be harvested
• The process of cloning a
human gene in a bacterial
plasmid can be divided into
six steps.
Plasmid
3. Mix the DNAs;
they join
by base-pairing
Recombinant
DNA
plasmid
Bacterial clones
carrying many
copies of the
human gene
Human
cell
2.Cut both
DNAs with
the same
restriction enzyme
4.Add DNA ligase
to bond the DNA
covalently
5. Put plasmid
into bacterium
6.Clone the
bacterium
Cloning of animals
• You have learned
about gene cloning
• Scientists are
perfecting the
technique for cloning
animals
Animal Cloning
• How its done:
a) obtain an egg cell from the female of the species to be
cloned.
b) remove the nucleus from the egg cell.
c) obtain a body cell from the species to be cloned.
d) remove the nucleus from this cell.
e) place the nucleus from the body cell into the egg cell.
f) place this cell into the uterus of the female of the
species to clone.
g) after the normal gestation period, the clone will be
born.
Cloning Animals
Problems with Cloning
• Cloning has a low success rate
• Cloned organisms often have a shortened life
span
• Cloning is incredibly expensive
Applications of DNA Technology
Recombinant DNA in
industry
•
Many species of bacteria have been
engineered to produce chemical compounds
used by humans.
•
Scientists have modified the bacterium E. coli
to produce the expensive indigo dye that is
used to color denim blue jeans.
•
The production of cheese, laundry detergents,
pulp and paper production, and sewage
treatment have all been enhanced by the use
of recombinant DNA techniques that increase
enzyme activity, stability, and specificity.
•
Production of renewable fuel sources is aided
by bacterial digestion of cellulose materials
Applications of biotechnology
Applications of DNA Technology
Recombinant DNA
in medicine
• Pharmaceutical companies
already are producing
molecules made by
recombinant DNA to treat
human diseases.
• Recombinant bacteria are used
in the production of human
growth hormone and human
insulin
–This lab equipment
is used to produce
a vaccine against
hepatitis B
Applications of DNA Technology
Recombinant DNA in
agriculture
• Crops have been developed that
are better tasting, stay fresh
longer, and are protected from
disease and insect infestations.
“Golden rice” has been genetically
modified to contain beta-carotene
Could GM organisms harm human health or the
environment?
• Genetic engineering involves
some risks
– Possible ecological damage
from pollen transfer between
GM and wild crops
• Weeds could also become more
drought tolerant, or herbicide
resistant
– Pollen from a transgenic variety
of corn that contains a pesticide
may stunt or kill monarch
caterpillars
Polymerase chain reaction
(PCR)
• method is used to amplify
DNA sequences
• The polymerase chain
reaction (PCR) can
quickly clone a small
sample of DNA in a
test tube
Initial
DNA
segment
Number of DNA molecules
The PCR method is used to amplify DNA
sequences
• The polymerase chain reaction (PCR) can quickly clone a small
sample of DNA in a test tube
• Advantages of PCR
Can amplify DNA from a small sample
Results are obtained rapidly
Reaction is highly sensitive, copying only the target sequence
• Repeated cycle of steps for PCR
Sample is heated to separate DNA strands
Sample is cooled and primer binds to specific target sequence
Target sequence is copied with heat-stable DNA polymerase
Biotechnology
Gel Electrophoresis
2006-2007
Gel electrophoresis
• A method of separating DNA
in a gelatin-like material using
an electrical field
– DNA is negatively charged
– when it’s in an electrical field it
moves toward the positive side
DNA
–

“swimming through Jello”
+
Many uses of restriction enzymes…
• Now that we can cut DNA with restriction
enzymes…
– we can cut up DNA from different people… or
different organisms…
and compare it
– why?
•
•
•
•
•
forensics
medical diagnostics
paternity
evolutionary relationships
and more…
Comparing cut up DNA
• How do we compare DNA fragments?
– separate fragments by size
• How do we separate DNA fragments?
– run it through a gelatin
– gel electrophoresis
• How does a gel work?
Gel Electrophoresis
DNA &
restriction enzyme
longer fragments
wells
power
source
gel
shorter fragments
+
completed gel
Running a gel
fragments of DNA
separate out based
on size
cut DNA with restriction enzymes
1
2
Stain DNA
– ethidium bromide
binds to DNA
– fluoresces under UV
light
3
Gel Electrophoresis- Components
• Separation technique: separates DNA by size and charge
• 1.Restriction enzymes
– cut DNA I into fragments
• 2. The gel
– “Wells” made at one end. Small amounts of DNA are placed in the wells
3. The electrical field
gel placed in solution and an electrical field set up with one neg. (-) & one
pos. (+) end
4. The fragments move
negatively charged DNA fragments travel toward positive end. The smaller
fragments move faster, larger particles move more slowly.
Mixture of DNA
molecules of
different sizes
Longer
molecules
Power
source
Gel
Shorter
molecules
DNA fingerprint
• Why is each person’s DNA pattern different?
– sections of “junk” DNA
• doesn’t code for proteins
• made up of repeated patterns
– CAT, GCC, and others
– each person may have different number of repeats
• many sites on our 23 chromosomes with
different repeat patterns
GCTTGTAACGGCCTCATCATCATTCGCCGGCCTACGCTT
CGAACATTGCCGGAGTAGTAGTAAGCGGCCGGATGCGAA
GCTTGTAACGGCATCATCATCATCATCATCCGGCCTACGCTT
CGAACATTGCCGTAGTAGTAGTAGTAGTAGGCCGGATGCGAA
Uses: Forensics
• Comparing DNA sample from crime scene
with suspects & victim
suspects
S1 S2 S3
crime
scene
V sample
–DNA

+
Electrophoresis use in forensics
• Evidence from murder trial
– Do you think suspect is guilty?
blood sample 1 from crime scene
blood sample 2 from crime scene
blood sample 3 from crime scene
“standard”
blood sample from suspect
OJ Simpson
blood sample from victim 1
N Brown
blood sample from victim 2
R Goldman
“standard”
Uses: Paternity
• Who’s the father?
–
DNA

+
Mom
F1
F2
child
Uses: Evolutionary relationships
• Comparing DNA samples from different
organisms to measure evolutionary
relationships
turtle snake rat squirrel
–
DNA

+
1
2
3
4
5
1
2
3
4
fruitfly
5
Uses: Medical diagnostic
• Comparing normal allele to disease allele
chromosome
with normal
allele 1
chromosome with
disease-causing
allele 2
–DNA

Example: test for Huntington’s disease
+
Diagnosis of genetic disorders
• The DNA of people with and without a genetic
disorder is compared to find differences that are
associated with the disorder. Once it is clearly
understood where a gene is located and that a
mutation in the gene causes the disorder, a
diagnosis can be made for an individual, even
before birth.
• Single nucleotide polymorphism (SNP) is a
variation at one base pair within a coding or
noncoding sequence
• Scientists hypothesize that SNP s may help
identify different types of genetic disorders
Diagnosing Genetic Disorders
– Amniocentesis- physicians remove a small amount of
amniotic fluid from the placenta. A karyotype can be made
from this fluid to check for possible disorders.
• Chorion villi sampling- physician analyzes a sample of the
chorion villi, which grows between the uterus and the
placenta. The villi will have the same DNA as the baby.
Mapping and Sequencing the Human
Genome In February of 2001, the HGP published its working
draft of the 3 billion base pairs of DNA in most human cells.
• The Human Genome
Project involves:
– genetic and physical
mapping of
chromosomes
– DNA sequencing
– comparison of
human genes
with those of
other species
Sequencing the human genome
• The difficult job of sequencing the human genome is
begun by cleaving samples of DNA into fragments
using restriction enzymes.
• Then, each individual fragment is cloned and
sequenced. The cloned fragments are aligned in the
proper order by overlapping matching sequences,
thus determining the sequence of a longer fragment.
The Human Genome Project revealed that most of
the human genome does not consist of genes
• Results of the Human
Genome Project
• Humans have 21,000 genes
in 3.2 billion nucleotide pairs
• Only 1.5% of the DNA codes
for proteins, tRNAs, or
rRNAs
• The remaining 88.5% of the
DNA contains:
– Control regions such as promoters
and enhancers
– Unique noncoding DNA
– Repetitive DNA
Applications of the Human Genome
Project
• Improved techniques for
prenatal diagnosis of human disorders,
– use of gene therapy,
– development of new methods of crime detection
are areas currently being researched.
– diagnosis of genetic disorders.
Gene therapy
• the insertion of normal
genes into human cells to
correct genetic disorders.
– Progress is slow,
however
– There are also ethical
questions related to
gene therapy
Proteomics is the scientific study of the full set of
proteins encoded by a genome
– Proteomics
– Studies the proteome, the complete set of proteins
specified by a genome
– Investigates protein functions and interactions
– The human proteome may contain 100,000 proteins
– Genomics
• The study of an organism’s complete set of genes and
their interactions
Copyright © 2009 Pearson Education, Inc.