Download 11-2 Genetics and Probability

Chapter 15 – Genetic Engineering
HOW AND WHY DO SCIENTISTS
MANIPULATE DNA IN LIVING CELLS?
SOME REASONS WHY:
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Increase the yield from plants and animals
(milk, beef, chicken, corn, soybeans, etc)
Disease and pest prevention/resistance
Cloning
Medical Research
Gene Therapy
Genetic Testing
Personal identification (DNA fingerprint)
15.1 Selective Breeding
Selective Breeding
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Taking advantage of naturally occurring genetic variations
to pass wanted traits to the next generation.
Methods used to selectively breed:
1. Hybridization – crossing dissimilar individuals to bring together
desirable characteristics from each
Ex. (disease resistance X food producing capacity)
2. Inbreeding – breeding individuals with similar characteristics to
ensure unique traits are preserved (pure bred dogs)
15.2 Recombinant DNA (Finding Genes)
Can we change the DNA of a
living cell?
1.
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Cut the DNA using restriction
enzymes
Build a DNA sequence with
the gene or genes desired
Enzymes like ligase connect
the sticky ends of two DNA
pieces together
Recombinant DNA – joining DNA
from two or more different sources
Plasmids and Genetic Markers
Problem: DNA molecules inserted
into host cells were not replicated:
Solution: Use plasmids to introduce
1. Plasmid – a piece of circular
bacterial DNA
2. Plasmids generally contain:
a. a replication start signal (ori),
b. restriction enzyme start site (EcoR1)
c. genetic markers like antibiotic
resistance genes (tetracycline and
ampicillin)
Plasmids and Genetic Markers
Recombination Process using Plasmids
1.
The same restriction enzyme is used to cut plasmid and DNA of interest
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The DNA of interest is joined to the plasmid using ligase
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Recombined DNA is inserted into the host cell
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The genetic marker (like antibiotic resistance) identifies the recombined
DNA after bacterial growth
Plasmids and Genetic Markers
Use for recombined genes:
Human growth hormone (HGH), insulin, gene therapy,
resistance of crops to pests and herbicides, pollution
control, designer species
Transgenic Organisms
Transgenic – organisms that
contain genes from other
species, produced by insertion
of recombinant DNA into the
genome of a host organism
Used in plants, animals and
microorganisms – increased
our understanding of gene
regulation
Genetically modified plants
Transgenic Organisms
Transgenic Plants – transformed by
using bacteria such as
Agrobacterium, removing the
cell wall or directly injected
Transgenic Animals – transformed
by injecting DNA directly into
the nucleus of egg cells.
In each case the goal is to have the
host cell combine the recombinant
DNA with it’s own chromosomes
Cloning
Clone – A member of a population of genetically identical cells produced from a
single cell
Steps in nuclear transplantation cloning:
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Nucleus of an unfertilized egg is removed
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Egg cell is fused with a donor cell that contains a nucleus
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The egg and donor cell are fused using an electric shock
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Diploid egg develops into an embryo
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Embryo is implanted in the uterine wall of a foster mother.
Animals cloned: frogs, sheep (Dolly 1997), cows, pigs, mice and cats
15.3 Applications of Genetic Engineering
Have you eaten genetically modified
(GM) foods this week?
GM Crops – transgenic plants that
resist pests, herbicides, disease
and result in increased yields.
-Use of these crops is on the rise
-Introduced in 1996 (soybean)
-As of 2007 GM crops made up
92% of soybeans, 86 % of cotton
and 80% of corn
Examples: Roundup ready soybeans,
Bt corn, tomatoes, rice, potatoes
15.3 Applications of Genetic Engineering
GM animals – engineered to increase
production, nutritional benefit or
product not typically associated with
that animal.
30% of milk in US is coming from
cows injected with bovine growth
hormone (BGH)
In 2008, US approved the sale of
meat and milk from cloned animals.
15.3 Applications of Genetic Engineering
Examples of GM foods:
Cows – BGH, increased milk output
Pigs – leaner meat, omega 3 acids
Salmon – GH, shorter time to market
Goats – spider genes to manufacture
silk, antibacterial goat milk
Gene Therapy
• Gene Therapy – an absent or faulty gene is replaced
by a normal, working gene.
– The first attempted of a gene transfer to cure a
disease occurred in 1990.
– Scientist engineer a virus to carry the new gene
into the target cells
– Problem: need reliable ways to insert working
genes in target cells and ensure DNA used does
no harm.
DNA Fingerprinting
1. Restriction enzymes are used to cut the DNA into fragments
containing genes and repeats
2. The restriction fragments are separated according to size
using gel electrophoresis
3. The DNA fragments containing repeats are then labeled using
radioactive probes. This labeling produces a series of bands –
the DNA fingerprint.
DNA Fingerprinting