Download Chapter 13: Genetic Engineering

Chapter 13: Genetic
Engineering
Selective Breeding
Has been occurring for thousands
of years Ex: (dog breeds,
agriculture)
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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
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hybrids are often hardier/stronger than
either parent
ex: mules (cross between horse and
donkey), ligers (lion/tiger)
Selective Breeding
Inbreeding: crossing two organisms that
are very similar to retain desirable
characteristics.
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Can lead to recessive genetic disorders
appearing frequently because the organisms
are so similar genetically.
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:
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Oil-eating bacteria- used to clean up oil spills
Creating polyploidy (3+ sets of chromosomes)
plants- usually larger and stronger
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Examples: bananas, citrus
Genetic Engineering
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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
How do they cut the pieces they
want?
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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)
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CTTAAG
GAATTC
is cut
CTTAAG
GAATTC
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The two ends are
known as “Sticky”
because they reattach
to a complementary
end very easily
because if chemical
attractions
How are the pieces identified?
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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
So what does that tell us?
relatedness of individuals (paternity
tests),
 relatedness of groups of organisms
(closest related species), or
 relatedness of DNA to suspects and
evidence in a crime scene.
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Genetic Engineering
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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?
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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?
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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)
Genetic Engineering
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We can now find and isolate certain genes.
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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
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Gene Therapy: a faulty gene is replaced
with a normal working gene
How do we get a lot of copies of a
specific DNA sequence we want?
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PCR- Polymerase Chain Reaction
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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
replicates sides, using both as
templates
Copies are made at an exponential
rate of only the desired gene
Recombinant DNA
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Manipulating the
presence or absence of
genes 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
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Transformation- a
cell takes in DNA
from outside the
cell and
incorporates it
into its own DNA
(bacterial
plasmids,
chromosomes in
plants and
animals)
Applications of Genetic
Engineering
Transgenic Organisms: organisms that
contain DNA from other species
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Transgenic bacteria:
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can produce human insulin (for diabetes)
human growth hormone
blood clotting factor (for hemophilia)
Transgenic Organisms
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Transgenic animals:
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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 Organisms
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Transgenic plants:
genetically modified foods
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seedless grapes and
watermelons
rice with vitamin enhancement
pest-resistant crops (so
chemical pesticides do not
need to be used)
Cloning
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Cloning: creating an
organism whose genes are
exactly the same as a
single parent
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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
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Scientists removing the Egg nucleus:
http://learn.genetics.utah.edu/content/tec
h/cloning/whatiscloning/images/enucleatio
n.mpg
Scientists inserting the donor somatic cell
nucleus into the empty egg:
http://learn.genetics.utah.edu/content/tec
h/cloning/whatiscloning/images/transfer.m
pg
Stem Cells
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Every cell in your body originated from single
cell (zygote) that was the fusion of egg and
sperm.
It divides into a mass of cells that do not yet
have a defined function- these cells are said to
be undifferentiated.
Cells that are undifferentiated can give rise to
many types of cells: blood cells, skin cells,
nerve cells, etc.
What is a stem cell? (click) 
Stem Cells- What is the difference?
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Let’s watch the stem cell animations.
Stem Cells
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Embryonic stem cells- cells from very
early stages of development that can
become ANY kind of cell, but they are
harder to manipulate and have the risk
of rejection by the recipient, ethical
objections because the embryo is
destroyed during the process of
harvesting the cells
Stem Cells
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Adult stem cells- cells from certain
region in our bodies that are only
partially differentiated and can be
manipulated into becoming a limited
kind of cell, less chance of being
rejected, fewer ethical objections
Stem Cells
All stem cells—regardless of their source—
have three general properties: they are
capable of dividing and renewing themselves
for long periods; they are unspecialized; and
they can give rise to specialized cell types.
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What is the purpose of stem cell therapy?
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To restore tissues that have been damaged by
injury or disease that cannot repair themselves
What are some concerns with this
new Biotechnology?
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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?
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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?
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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?