Download Chapter 15 Genetics Engineering

Chapter 15
Genetics Engineering
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15.1 Selective Breeding
S Selective breeding:
S Allowing only those animals with wanted characteristics to
produce the next generation.
S What are some things that are used for selective breeding?
Hybridization
S Luther Burbank was one of the first selective breeders. He
developed over 800 varieties of plants. He did this by using
hybridization. The disease resistance of one plant would
combine with the food producing capacity of another. This
allowed farmers to produce more food.
S Hybridization:
S Crossing dissimilar individuals to bring together the best of
both organisms.
S Inbreeding:
S The continued breeding of individuals with similar
characteristics.
S Think of dogs and trophy animals.
Increasing Variation
S Breeders can increase the genetic variation in a population
by introducing mutations, which are the ultimate source of
biological diversity.
S Biotechnology:
S The application of a technological process, invention, or
method to living organisms.
S What are some things that can cause mutations which can
cause diversity?
S Radiation or chemicals.
S Breeders can increase the mutation rate by using radiation
or chemicals.
S Many mutations are harmful, with luck and perseverance
scientists can use some mutated organisms.
S Best example would be bacteria, scientist are able to modify
bacteria, to create bacteria strains.
15.2 Recombinant DNA
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In 1987, Douglas Prasher, a biologist at Woods Hole
Oceanographic Institute in Massachusetts, wanted to find a
specific gene in a jellyfish that codes for a molecule called green
fluorescent protein, or GFP.
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This natural protein, found in the jellyfish, absorbs energy from
light and makes parts of the jellyfish glow.
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Prasher thought that GFP from the jellyfish could be linked to a
protein when it was being made in a cell, a bit like attaching a
light bulb to that molecule.
Finding Genes
S GFP – Green Fluorescent
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Protein
Isolated from jellyfish
Used to label or ‘mark’
other proteins.
The GFP gene is added to
other genes
Weird, but useful results:
http://youtu.be/Sl2PRHGpYuU
Finding Genes
S To find GFP:
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Restriction fragments separated by gel electrophoresis
Find the one fragment that binds tightly to a corresponding
molecule of mRNA
Southern blotting, named after its inventor, Edwin
Southern, used to identify the GFP gene
Today, it’s quicker and easier to find genes in databases
because the DNA of many organisms has been sequenced
S How do scientists copy the DNA of living organisms?
S Polymerase chain reaction (PCR):
S The technique used by biologists to make copies of a
particular gene.
Polymerase Chain Reaction
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Polymerase chain
reaction (PCR) allows
scientists to make many
copies of a gene
S 1. A piece of DNA is heated,
which separates its two
strands.
Polymerase Chain Reaction
S 2. Add a primer so that DNA
polymerase knows where to
bind and start working
Polymerase Chain Reaction
S 3. DNA polymerase copies
the gene. These copies then
serve as templates to make
more copies.
S 4. Several dozen cycles can
produce billions of copies
The DNA Polymerase
S Most DNA polymerase is denatured at high temperature
S Polymerase used in PCR is from bacteria that live in hot springs
Changing DNA
S Recombinant DNA:
S Joining together DNA from two or more sources.
S This can create a change in genetic composition of living
organisms.
Combining DNA Fragments
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A gene from one organism can be attached to the DNA of
another organism.
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Restriction enzymes cut DNA at specific sequences,
producing “sticky ends,” which are single-stranded
overhangs of DNA.
Combining DNA Fragments
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If two DNA molecules are cut with the same restriction
enzyme, their sticky ends will bond to a DNA fragment that
has the complementary base sequence. DNA ligase then
joins the two fragments.
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The resulting molecules are called recombinant DNA.
S Plasmids:
S Small circular DNA molecules.
S Joining DNA to a plasmid, and then using the
recombinant plasmid to transform bacteria, results in
the replication of the newly added DNA along with the
rest of the cell’s genome.
S The recombinant plasmid has a genetic marker, such as
a gene for antibiotic resistance
S Genetic marker:
S Joining DNA to a plasmid, and then using the recombinant
plasmid to transform bacteria, results in the replication of the
newly added DNA along with the rest of the cell’s genome.
Transgenic Organisms
S How can genes from one organism be inserted into another
organism?
S Transgenic organisms can be produced by the insertion of
recombinant DNA into the genome of a host organism.
S Transgenic:
S Organisms that contains genes from another organism.
S The universal nature of the genetic code makes it possible to
construct organisms that are transgenic, containing genes
from other species.
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Like bacterial plasmids, the DNA molecules used for
transformation of plant and animal cells contain genetic
markers that help scientists identify which cells have been
transformed.
S By examining the traits of a genetically modified organism, it is
possible to learn about the function of the transferred gene.
Transgenic Animals
S Scientists can transform animal cells using some of the same
techniques used for plant cells.
S The egg cells of many animals are large enough that DNA can
be injected directly into the nucleus.
S Once the DNA is in the nucleus, enzymes that are normally
responsible for DNA repair and recombination may help insert
the foreign DNA into the chromosomes of the injected cell.
S What was the first animal to be cloned?
S Clones of animals were first produced in 1952 using
amphibian tadpoles.
S What was the first animal to be cloned that you heard of ?
S Dolly the sheep
S When did this happen?
S July 5th, 1996
S Did she die?
S February 14th, 2003
S Clone:
S Member of a population of genetically identical cells
produced from a single cell.
S The technique of cloning uses a single cells from an adult
organism to grow an entirely new individual that is
genetically identical to the organism from which the cell was
taken.
Steps in Cloning
S 1. The nucleus of an unfertilized egg cell is removed.
S 2. Next, the egg cell is fused with a donor cell that contains a
nucleus, taken from an adult.
S 3. The resulting diploid egg develops into an embryo, which is
then implanted in the uterine wall of a foster mother, where it
develops until birth.
S 4. Cloned cows, pigs, mice, and even cats have since been
produced using similar techniques.
15.3 Applications of Genetic
Engineering
S How can genetic engineering benefit agriculture and
industry?
S Genetic modification could lead to better, less expensive,
and more nutritious food as well as less-harmful
manufacturing processes.
GM Crops
S Since 1996, GM plants have been an important component
of our food supply.
S GM crops made up 92% of soybeans, 86% of cotton, and
80% of corn grown in the United States.
S GM have Bt toxin, which kills insects, and is harmless to
animals and humans.
GM Animals
S About 30% of our milk have come from cows that have
been injected with hormones .
S Use growth hormones to grow salmon more quickly.
S In Canada, scientists combined spider genes into the cells of
lactating goats, the goats began to manufacture silk along
with their milk.
Health and Medicine
S How can recombinant-DNA technology improve human
health?
S Preventing disease
S Medical research
S Treating disease
S Genetic testing
S Gene therapy:
S Process of changing a gene to treat a medical disease or
disorder.
S An absent or faulty gene is replaced by a normal, working
gene. Gene therapy allows the body to make the protein or
enzyme it needs, which eliminates the cause of the disorder.
Examining Active Genes
S DNA microarray:
S Studies hundreds or even thousands of genes at once to
understand their activity level.
S Scientists can study which cells are active or inactive and
what their functions are.
S If you commit a crime, what are something's you do not
want to leave behind?
S DNA, fingerprints…. Etc
S DNA fingerprinting:
S Analyzes sections of DNA that may have little or no
function but that vary widely from one individual to
another.
DNA fingerprinting
S Forensics:
S The scientific study of crime scene evidence.
S DNA evidence has saved more than 110 wrongfully
convicted prisoners from death sentences.
Who is this guy?
What does he say?