Chapter 9: Genetic
Engineering
Why do these pigs glow in the
dark?
Normal pig genes + GFP jelly fish gene
+
GFP = Green Fluorescent “Pig”ment
Selective Breeding
•
Has been occurring for thousands
of years Ex: (dog breeds,
agriculture)
–
–
Takes advantage of naturally
occurring traits in a population
Two types
Selective Breeding
•
Hybridization: crossing two dissimilar
organisms to get the best traits of both
organisms
–
–
hybrids are often hardier/stronger than
either parent
ex: mules (cross between horse and
donkey), ligers (lion/tiger)
LIGER
• Male lion + female tiger
Tigon
• Male tiger + female lion
Leopon
• Male Leoplard + female lion
Mule
• Male donkey + female horse
Hinny
• Male horse + female donkey
Huck
• Male horse + female duck
Sea Rex
• Female T-Rex + male sea horse
Turger
• Male turtle + cheese burger
Selective Breeding
•
Inbreeding: crossing two organisms that
are very similar to retain desirable
characteristics.
–
Can lead to recessive genetic disorders
appearing frequently because the
organisms are so similar genetically.
•
–
Why would recessive genetic disorders be seen
more often?
Ex. Maintaining “purebred” dog breeds
Increasing Variation
•
If the desired characteristic is not
present, scientists have induced
mutations in hope of it causing the
right effect
Success stories:
•
–
Oil-eating bacteria- used to clean up oil
spills
Creating polyploidy (3+ sets of
chromosomes) plants- usually larger and
stronger
–
•
Examples: bananas, citrus
Genetic Engineering
•
That was the “old” way
of manipulating
inheritance. Now, we
can isolate specific
DNA sequences and
modify the code in
what is called genetic
engineering.
How do they get it out of the cells?
o DNA extraction- lysing the cells and
separating the excess cell parts from the DNA
by using a centrifuge
Dissolved DNA
cell junk
Restriction enzymes cut DNA.
• Restriction enzymes act as “molecular
scissors.”
– come from various types of bacteria
– allow scientists to more easily study and
manipulate genes
– cut DNA at a specific nucleotide sequence
called a restriction site
How do they cut the pieces they
want?
• Restriction enzymes- they cut DNA at a
specific site
– (100s of them that identify different
sequences of base pairs know as recognition
sequences- they are a palindrome- read the
same 5’-3’ in each direction)
– CTTAAG is cut
CTTAAG
GAATTC
GAATTC
– some cut straight across and leave “blunt ends”
– some make staggered cuts and leave “sticky ends”
– Sticky Ends – refers to
the two ends of DNA
after being cut by a
restriction enzyme
because they reattach
to a complementary
end very easily
because of chemical
attractions
How are the pieces identified?
• Using gel electrophoresis
• Different fragments end up being different
lengths
• They are run through gel electrophoresis where
electrical current pull DNA fragments through an
agarose gel. DNA mixtures are placed in a well
in agarose and electrical current is switched on.
• The small fragments travel faster, and the
larger fragments cannot travel as far.
DNA fingerprint
produced by gel
electrophoresis
•
Different restriction enzymes cut DNA in different ways.
– each enzyme has a different restriction site
– Smaller fragments move faster and travel farther than larger
fragments.
– Fragments of different sizes
appear as bands on the gel.
•
A restriction map shows the lengths of DNA fragments between restriction sites.
– only indicate size, not DNA
sequence
– useful in genetic engineering
– used to study mutations
A DNA fingerprint is a type of restriction map.
• DNA fingerprints are based on parts of an individual’s
DNA that can by used for identification.
–
–
–
–
based on noncoding regions of DNA
noncoding regions have repeating DNA sequences
number of repeats differs between people
banding pattern on a gel is a DNA fingerprint
DNA fingerprinting is used for identification.
• DNA fingerprinting depends on the
probability of a match.
– Many people have the
same number of
repeats in a certain
region of DNA.
– The probability that two
people share identical
numbers of repeats in
several locations is
very small.
(mother) (child 1) (child 2) (father)
– Individual probabilities are multiplied to find the overall probability of
two DNA fingerprints randomly matching.
1 x 1 x 1 =
1
= 1 chance in 5.4 million people
500 90 120
5,400,000
– Several regions of DNA are used to make
DNA fingerprints.
•
DNA fingerprinting is used in several ways.
–
–
–
–
evidence in criminal cases
paternity tests
immigration requests
studying biodiversity
– tracking genetically
modified crops
Genetic Engineering
•
Gene sequencing: using a gel
electrophoresis method ()
or using a machine (below),
scientists can figure out genes and
entire genomes (all the genes in an
organisms)
How can we sequence DNA?
• Mix unknown DNA fragment with DNA
polymerase and nucleotides to copy the DNA.
• The nucleotides added will also have special
dideoxynucleotides (didNTP) with attached dyes.
• Newly synthesized DNA will be made but will
stop each time a didNTP nucleotide is added.
How can we sequence DNA?
• The DNA is run on a gel and the
fragments will make a colored banding
pattern in the order of bases (A, T, G, or
C)
• Watch the animation on the website
highlighted in the resources page of my
website.
Genetic Engineering
–
We can now find and isolate certain genes.
•
•
•
–
you can test for certain genetic disorders, and
predict chances of inheritance
scientists can study the gene’s function and how
to treat people with the genetic disorder
Ex: what gene causes diabetes? Breast cancer?
We have completed the Human Genome
Project mapping all human genes
Gene Therapy
•
•
Gene Therapy: a faulty gene is replaced
with a normal working gene
See a real gene therapy success story
with a blind dog (click)
How do we get a lot of copies of a
specific DNA sequence we want?
• PCR- Polymerase Chain
Reaction
– a primer is added to the beginning of the
isolated desired gene
– DNA is heated to break the hydrogen
bonds between the nitrogenous bases
– DNA polymerase attaches and replicated
sides, using both as templates
– Copies are made at an exponential rate
of only the desired gene (much faster
than cloning)
PCR uses polymerases to copy DNA
segments.
• PCR makes many copies of a specific DNA
sequence in a few hours.
target sequence of DNA
• PCR amplifies DNA samples.
• PCR is similar to DNA replication.
• Each PCR cycle doubles the number of
DNA molecules.
Recombinant DNA
• Manipulating the
presence or absence of
a gene by adding or
cutting out gene
sequences
• Combining DNA from two
different sources by
cutting with the same
restriction enzymes
creates DNA that has
been modified
• Transformation- a
cell takes in DNA
from outside the
cell and
incorporates it
into its own DNA
(bacterial
plasmids,
chromosomes in
plants and
animals)
New genes can be added to an
organism’s DNA.
• Recombinant DNA contains genes from
more than one organism.
(bacterial DNA)
•
Bacterial plasmids are often used to make recombinant DNA.
– plasmids are loops of DNA in
bacteria
– restriction enzymes cut plasmid
and foreign DNA
– foreign gene inserted into plasmid
Genetic engineering produces
organisms with new traits.
• A transgenic organism has one or more
genes from another organism inserted
into its genome.
Applications of Genetic Engineering
Transgenic bacteria:
•
•
•
can produce human insulin (for
diabetes)
human growth hormone (for
Turner’s syndrome)
blood clotting factor (for
hemophilia)
Transgenic Organisms
•
Transgenic animals:
– study human genes in animals
– produce organisms that can make
human proteins
– cows that can grow faster with
multiple copies of growth hormone
A natural protein produced
in the milk of GEM and
other transgenic cows kills
the bacteria that cause
mastitis.
•
Transgenic animals are used to study diseases and gene functions.
– transgenic mice used to study development and disease
– gene knockout mice used to study gene function
Transgenic Organisms
•
Transgenic plants:
genetically modified foods
– seedless grapes and
watermelons
– rice with vitamin enhancement
– pest-resistant crops (so
chemical pesticides do not
need to be used)
•
Scientists have concerns about some uses of genetic engineering.
– possible long-term health effects of eating GM foods
– possible effects of GM plants on ecosystems and biodiversity
TRANSGENIC ORGANISM GONE WRONG!!
Cloning
–
Cloning: creating an
organism whose genes are
exactly the same as a
single parent
•
•
All bacteria and organisms
that reproduce asexually are
technically clones
Multicellular organisms are
not as easy to clone- a
mammal was cloned officially
in 1997—Dolly
Cloning
• The nucleus of an adult, donor egg is removed
• This empty egg is fused with another adult
somatic cell’s NUCLEUS (diploid, 2N)
• The cell is stimulated with electric shock to divide
normally by mitosis and the zygote is implanted
into a surrogate mother
• The baby is born of the surrogate and has the
EXACT same genes as the organism who
donated the 2N nucleus.
The difference between regular
reproduction and cloning  (click)
Cloning videos
• Scientists removing the Egg nucleus:
• http://learn.genetics.utah.edu/content/cloni
ng/whatiscloning/
Cloning- practice
• Clone Mimi the mouse! (click)
Genetics provides a basis for new medical treatments.
Genetic screening can detect genetic
disorders.
• Genetic screening involves the testing of DNA.
– determines risk of having
or passing on a genetic
disorder
– used to detect specific
genes or proteins
– can detect some genes
related to an increased
risk of cancer
– can detect some genes
known to cause genetic
disorders
DMD
N
Gene therapy is the replacement of
faulty genes
• Gene therapy replaces defective or
missing genes, or adds new genes, to
treat a disease.
• Several experimental techniques are used for gene
therapy.
– genetically engineered viruses used to
“infect” a patient’s cells
– insert gene to stimulate immune system to
attack cancer cells
– insert “suicide” genes into cancer cells that
activate a drug
What are some concerns with this
new Biotechnology?
• Ethics: moral principles and values that a
society should adhere to in determining the
use of scientific discoveries
What are some concerns with this
new Biotechnology?
• What is ethically acceptable to use while testing on
animals?
• What could genetically modified crops do to the
environment?
• What does consuming genetically modified food do to
us long term?
What are some concerns with this
new Biotechnology?
• Once able to find and fix faulty genes with gene
therapy, what is the line we draw on fixing genes?
Could we fix not only faulty genes, but undesirable
ones?
• Could we choose our children’s eye color?
• If we can test for genetic disorders at birth, who can
access this information? Could discrimination occur
based on your genes?