Chapter 13 – Genetic Engineering

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Transcript Chapter 13 – Genetic Engineering

Chapter 13
Genetic Engineering
Selective Breeding
• Choose organisms with the desired traits
and breed them, so the next generation also
has those traits
• Nearly all domesticated animals and crops
A “Hybrid”
• Breed two dissimilar organisms
• In plants – often results in better lines – hybrids are larger, stronger,
• In animals – hybrids produced may be weaker and sterile
– Ex – wolf x dog ---- weak wolf-dog
– Ex – horse x donkey ---- mule (sterile)
Lion x Tiger = Liger
Horse x Donkey = Mule
• Breeding two organisms that are
very similar to produce offspring
with the desired traits.
– Ex – dog breeds
•Risks – might bring together two
individuals that carry bad recessive genes –
many purebred dogs have genetic disorders
that mutts don’t get.
Increasing Variation
• Induce mutations – the ultimate source of
genetic variations among a group of
– Mutagens used – radiation and chemicals
– Some organisms are formed that have more
desirable variations.
Producing new kinds of
• Can expose millions of bacteria at one time
to radiation – increases chances of
producing a successful mutant.
– Ex – bacteria that can digest oil have been
produced this way
Producing new kinds of plants:
• Drugs that prevent chromosomal separation
in meiosis have been used to create plants
that have more than two sets of
chromosomes (2n). These are called
polyploid plants.
– Ex – bananas, citrus fruit, strawberries, many
ornamental flowers
Diploid corn
Tetraploid corn
Manipulating DNA – tools of
the molecular biologist
• DNA extraction – open the cells and
separate DNA from all the other cell parts.
• Separating DNA – Gel Electrophoresis
– Place fragments at one end of a porous gel – we
use agarose gel
– Apply an electric current – The DNA is
negatively charged and will travel toward the
positive end of the gel.
– The larger pieces of DNA move slower, the
smaller ones faster.
– Used to compare genomes of different
organisms or different individuals.
– Also used to locate and identify one particular
gene out of an individual’s genome.
Click here for animation about
gel electrophoresis
Using the DNA Sequence
• Sequence can be read, studied, and
Cell Transformation
• A cell takes in DNA from outside the cell
and that DNA then becomes part of the
cell’s DNA.
• Bacteria – place DNA in the solution that
bacteria live in, and some of that DNA will
be taken in by the bacteria cells.
Transforming Animal Cells
– Directly inject DNA into the nucleus of an egg
– it will become part of the chromosomes.
• Has been used to replace specific genes.
Glowing mouse cells in
embryos that were made
from sperm given the gene
for bioluminescence from
jellyfish – now all the cells
Applications of Genetic
• Gene for luciferase was isolated from
fireflies and inserted into tobacco plants –
they glowed!
• Transgenic organisms – contain genes
from other species
A transgenic mouse, which carries
a jellyfish gene, glows green under
fluorescent light.
Transgenic Organisms
• Bacteria - Make human proteins like
• Plants – 52% of soybeans, 25% of corn in
US in year 2000. Some produce natural
insecticide, some resist weed-killers, may
soon be used to produce human antibodies;
rice with vitamin A.
•Animals – mice with immune
systems like humans:
Farm animals that grow faster
and larger with extra copies of
growth hormone genes;
Animals with leaner meat
Chickens resistant to bacterial
• Clone – member of a population
of genetically identical cells
produced from a single cell.
• 1996 – Dolly cloned –
1st mammal (sheep) cloned.
• She got arthritis several years
earlier than most sheep
• Died in 2003
• Reproductive cloning would present the
potential of creating a human OR animal
that is genetically identical to another
person who has previously existed (maybe
extinct) or who still exists
good or bad?
• May conflict with long-standing religious
and societal values about human dignity,
possibly infringing upon principles of
individual freedom, identity and autonomy
• Therapeutic cloning would require the
destruction of human embryos in the test
• Opponents argue that
using this technique to
collect embryonic stem
cells is wrong, regardless
of whether such cells are
used to benefit sick or
injured people.
The Goods!! 
• Therapeutic cloning WOULD offer the
potential for treating humans suffering from
disease or injury
• Could help sterile couples
fulfill their dream of
The Goods!!
• Human cloning is also a GREAT way to
avoid passing on a bad gene that runs in the
family without having to undergo embryo
screening or embryo selection
• “knock out” the bad genes… good or bad??
Ethics… Its
your call…