Environmental Influence and
Genetic Technology
Differentiation
•
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
Differentiation
•
This is the process
followed by stem cells
–
Undifferentiated cells that
can differentiate into any
other cell
–
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
Norm of Reaction
•
Varied environments
create:
–
Range
of phenotypes
–
Within genetic potential
–
Reaction
with environment
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 Technology
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.
•
Section Objectives
•
Evaluate the importance of plant and animal
breeding to humans.
•
Explain a testcross.
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
How do we do mix genes?
•
Genetic engineering
–
Locate the desired
gene
–
cut
the DNA
in both organisms
–
paste
gene from one creature into other creature’s
DNA
–
insert
new chromosome into organism
–
organism
copies
new gene as if it were its own
–
organism
reads
gene as if it were its own
–
organism produces NEW protein
:
Remember: we all use the same genetic code!
R
ecombinant 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
Cutting DNA
•
DNA “scissors”
–
enzymes that cut DNA
–
restriction enzymes
•
used by bacteria to cut up DNA of
attacking viruses
•
EcoRI
,
HindIII
,
BamHI
–
cut DNA at specific sites
•
enzymes look for specific base sequences
GTAAC
GAATTC
ACGC
TT
CATTG
CTTAAG
TGCG
AA
GTAAC
G
|
AATTC
ACGC
TT
CATTG
CTTAA
|
G
TGCG
AA
Restriction enzymes
•
Cut DNA at specific sites
–
leave “sticky ends”
GTAAC
G AATTC
ACGCTT
CATTG
CTTAA G
TGCGAA
GTAAC
GAATTC
ACGC
TT
CATTG
CTTAAG
TGCG
AA
restriction enzyme cut site
restriction enzyme cut site
Sticky ends
•
Cut other DNA with same enzymes
–
leave “sticky ends” on both
–
can glue DNA together at “sticky ends”
GTAAC
G AATTC
ACGCTT
CATTG
CTTAA G
TGCGAA
gene
you want
GGACCT
G AATTC
CGGATA
CCTGGA
CTTAA G
GCCTAT
chromosome
want to add
gene to
GGACCT
G AATTC
ACGCTT
CCTGGA
CTTAA G
TGCGAA
combined
DNA
Sticky ends help glue genes together
TTGTAAC
GAATTC
TACGAATGGTTACATCGCC
GAATTC
A
CGCTT
AACATTG
CTTAAG
ATGCTTACCAATGTAGCGG
CTTAAG
T
GCGAA
gene you want
cut sites
cut sites
AATGGTTACTTGTAAC
G
AATTC
TACGATCGCCGATTCAACGCTT
TTACCAATGAACATTG
CTTAA
G
ATGCTAGCGGCTAAGTTGCGAA
chromosome want to add gene to
cut sites
AATTC
TACGAATGGTTACATCGCC
G
G
ATGCTTACCAATGTAGCGG
CTTAA
isolated gene
sticky ends
chromosome with new gene added
TAAC
GAATTC
TACGAATGGTTACATCGCC
GAATTC
TACG
ATC
CATTG
CTTAAG
ATGCTTACCAATGTAGCGG
CTTAAG
ATG
CTAGC
sticky ends stick together
DNA
ligase
joins the strands
Recombinant
DNA molecule
Why mix genes together?
TAAC
GAATTC
TACGAATGGTTACATCGCC
GAATTC
TACG
ATC
CATTG
CTTAAG
ATGCTTACCAATGTAGCGG
CTTAAG
ATG
CTAGC
•
Gene produces protein in different
organism or different individual
aa
aa
aa
aa
aa
aa
aa
aa
aa
aa
“new” protein from organism
ex:
human insulin from bacteria
human insulin gene in bacteria
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.
Plasmids
Vectors transfer DNA
•
Two mechanical vectors carry foreign DNA into a
cell
’
s nucleus
•
One,
a micropipette
, is inserted into a cell; the other
is a microscopic metal bullet coated with DNA that is
shot into the cell from a
gene gun.
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
+
transformed
bacteria
gene from
other organism
plasmid
cut DNA
recombinant
plasmid
vector
glue DNA
Grow bacteria…make more
grow
bacteria
harvest (purify)
protein
transformed
bacteria
plasmid
gene from
other organism
+
recombinant
plasmid
vector
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.
1.
.
Isolate DNA
from two sources
2
.Cut both
DNAs
with
the same
restriction enzyme
3. Mix the
DNAs
;
they join
by base
-
pairing
4.Add DNA ligase
to bond the DNA
covalently
5.
Put plasmid
into bacterium
6.Clone the
bacterium
Recombinant
DNA
plasmid
Human
cell
Plasmid
Bacterial clones
carrying many
copies of the
human gene
Cloning of animals
•
You have learned
about
gene cloning
•
Scientists are
perfecting the
technique for cloning
animals
Applications of biotechnology
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 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
Number of DNA molecules
Initial
DNA
segment
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
2006
-
2007
Biotechnology
Gel Electrophoresis
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
longer fragments
shorter fragments
power
source
completed gel
gel
DNA &
restriction enzyme
wells
-
+
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”
Running a gel
1
2
cut DNA with restriction enzymes
fragments of DNA
separate out based
on size
3
Stain DNA
–
ethidium bromide
binds to DNA
–
fluoresces under UV
light
Gel
Electrophoresis
-
sorts DNA molecules by size
•
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
Gel
Longer
molecules
Shorter
molecules
Power
source
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
GCTTGTAACGGCCT
CATCATCAT
TCGCCGGCCTACGCTT
CGAACATTGCCGGA
GTAGTAGTA
AGCGGCCGGATGCGAA
GCTTGTAACGG
CATCATCATCATCATCAT
CCGGCCTACGC
TT
CGAACATTGCC
GTAGTAGTAGTAGTAGTA
GGCCGGATGC
GAA
Uses: Forensics
•
Comparing DNA sample from crime scene
with suspects & victim
–
+
S1
DNA
S2
S3
V
suspects
crime
scene
sample
Electrophoresis use in forensics
•
Evidence from murder trial
–
Do you think suspect is guilty?
“standard”
blood sample 3 from crime scene
“standard”
blood sample 1 from crime scene
blood sample 2 from crime scene
blood sample from victim 2
blood sample from victim 1
blood sample from suspect
OJ Simpson
N Brown
R Goldman
Uses: Paternity
•
Who’s the father?
+
DNA
child
Mom
F1
F2
–
Uses: Evolutionary relationships
•
Comparing DNA samples from different
organisms to measure evolutionary
relationships
–
+
DNA
1
3
2
4
5
1
2
3
4
5
turtle
snake
rat
squirrel
fruitfly
Uses: Medical diagnostic
•
Comparing normal allele to disease allele
chromosome with
disease
-
causing
allele 2
chromosome
with normal
allele 1
–
+
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.
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