Chapter 13
Genetic Engineering
Changing the living world
Selective Breeding
Corn is one of the earliest know species of genetic engineering.
Ancient Pueblo Indians took the seeds from a native grass and saved
only the largest seeds to be planted in the spring.
This practice continued for thousands of years. The original plant is
believed to be extinct, but the modern corn plant flourishes.
Selective Breeding
By allowing only those organisms with desired characteristics to produce offspring,
humans have produced many different breeds.
Other types of selective breeding...
Hybrids – crossing two
different individuals
offspring often hardier
than their parents
Horse
+
Donkey
=
Mule
Inbreeding – continued breeding of individuals
with similar characteristics.
Dog breeds are maintained by inbreeding, but has risks.
Genetic defects can be expressed by recessive alleles
Increasing variation – introducing mutations
can increase diversity
Radiation and chemicals can cause mutations
DNA extraction
Gel Electrophoresis
•Enzymes cut DNA into fragments
•DNA fragments are poured onto a gel
•Electric voltage moves the DNA fragments across the gel
•Because longer segments move across the gel more slowly, and do not go as far
•Based on size, the DNA fragments make a pattern of bands on the gel
Cell Transformation
During transformation, a cell takes in
DNA from outside the cell, and
becomes part of the cell’s DNA.
The foreign DNA is first joined to a small,
circular DNA known as a plasmid.
Plasmids are found naturally in some bacteria and
have been very useful for DNA transfer.
Why?
The plasmid has a genetic “marker”... a gene to
distinguish which bacteria carry the foreign DNA.
How?
We use genes for antibiotic resistance as markers!
Applications of Genetic Engineering
Genes responsible for making fireflies
glow are inserted into a plant
Transgenic organisms –
contain DNA from different
organisms
This demonstrates how
closely related we all are!
Genetic engineering has spurred the growth of
biotechnology, a new industry that is changing
the way we interact with the living world
Mice produced with human genes that simulate our
immune system. This allows us to study human diseases.
Cloning
Dolly
1997
The first mammal cloned
from an adult cell
Cloning pets?
The first commercially cloned pet was a cat named
“Little Nicky” in 2004
Can you really have a beloved pet back?
See text p. 332