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Chapter 13
Genetic Engineering
Selective Breeding
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Passing on desired characteristics to the
next generation.
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Examples: different breeds of domestic and
farm animals, different varieties of plants
(corn, soybeans, potatoes, apples, etc.)
Inbreeding vs. Hybridization
Hybridization – crossing unlike individuals
to get the best of both organisms.
 Inbreeding – crossing organisms of similar
characteristics to maintain those
characteristics.

Inbreeding increases the chances of two
recessive alleles for a genetic defect being
passed on.
 This has led to joint problems and
blindness in German shepherds and
golden retrievers.

Increasing Variation
Breeders induce or cause mutations to
create genetic variability.
 What are mutations?
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Inheritable changes in DNA.
Breeders use radiation and chemicals to
induce mutations.
Increasing Variation
Breeders can increase genetic variation in
a population by inducing mutations.
 This creates genetic variability.
 A mutation is a change in DNA that can be
passed on to offspring.
 The mutation rate is sped up by using
chemicals and/or radiation.

This technique has worked well with
bacteria because millions of organisms
can be treated at once.
 This has led to hundreds of useful strains
of bacteria.
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Enzyme Name
alpha-amylase
GE Organism Use (examples)
bacteria
converts starch to simple
sugars
catalase
fungi
reduces food deterioration,
particularly egg-based
products
chymosin
bacteria/fungi clots milk protein to make
cheese
cyclodextrin-glucosyl transferase
bacteria
starch/sugar modification

Isomerase
bacteria

glucose oxidase
fungi

xylanase (hemicellulase)
bacteria/fungi
converts glucose sugar to
fructose sugar
reduces food deterioration,
particularly egg-based
products
enhances rising of bread
dough
Another method of genetic engineering is
forced polyploidy.
 Scientists use drugs that prevent
chromosomal separation to increase the
normal number of chromosomes.
 In animals, this is usually fatal, but many
plants benefit from this and produce larger
crops.

13-2 Manipulating DNA

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DNA Extracting – cell is opened and the DNA is
separated from the other cell parts.
Cutting DNA – restriction enzymes are used like
scissors to cut the DNA at specific nucleotide
sequences.
Each restriction enzyme looks for a unique
sequence.
Separating DNA – gel electrophoresis is used to
separate DNA fragments based on their charge
and size.
What do you do with the DNA now?
Scientists attach dye to the nitrogenous
bases. When the base is used in
replication, it terminates the strand.
 Then the dye-tagged fragments are
separated using gel electrophoresis.
 Using this method, researchers can
determine DNA sequences and study an
organisms genes.
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When researchers study genes, they often need
to make copies to speed up the process.
This is done using polymerase chain reaction or
PCR.
DNA is heated to cause the strands to separate,
then cooled to allow replication to take place.
This is done multiple times to make thousands
or millions of copies of a gene. (Each time you
double the number.)
13-3 Cell Transformation
During cell transformation, a cell
incorporates DNA from outside the cell
into its own DNA.
 A common example of this is Genetically
engineered bacteria.
 Draw diagram on the board.

13-4 Applications
Transgenic Organisms – organisms
containing genes from another species.
 Examples: bacteria that contain genes for
Human Growth Hormone, insulin, clotting
factor, etc.
 Transgenic animals that grow faster and
leaner, and plants that are disease
resistant and produce higher yields.

Cloning
1997 – Ian Wilmut successfully cloned a
sheep named Dolly.
 Since then, cows, pigs, and mice have
been cloned using similar techniques.
 Cloned animals have a record of suffering
from genetic defects and health problems.

Restriction Enzymes
1.
2.
Definition – used as molecular scalpels
(scissors) to cut DNA in a precise &
predictable manner.
Most restriction enzymes scan a DNA
molecule looking for a specific sequence
of 4 or 6 nucleotides (usually a
palindrome site) ex: madam im adam,
radar, hannah, GGCTCGG,
ACTAGATCA, etc.
3.
4.
5.
They are naturally occurring enzymes
(proteins) found in bacteria and other
organisms. Used by bacteria to slice &
inactivate potentially dangerous DNA
(virus).
Over 600 of these enzymes have been
identified.
Native (self) DNA is protected from being
cut.
6.
Named after organisms they are
extracted from.
a.
b.
c.
ECO RI Escherichia coli strain RY13 1st one
isolated.
Bam HI Bacillus amyloliquifaciens strain H
1st one isolated.
Hind III Haemophilus influenzae strain Rd
3rd one isolated.
Plasmids
1.
2.
Definition – small rings of DNA.
Recombinant DNA (rDNA): contains
DNA from 2 different sources.
Gel Electrophoresis
1.
2.
Definition – technique used to separate
molecules based on charge, size &
shape. (DNA, RNA, Proteins)
Medium used: agarose – a
polysaccharide derivative of agar. The
gel is clear and resilient – a thick jello but
with pores to allow the molecules
through.
3.
4.
5.
6.
Movement through gel: faster movement:
smaller particles, greater charge, more
compact shape.
Samples are placed in a well in the
agarose slab.
The electrophoresis buffer (fluid)
contains electrolytes that will allow
electricity to conduct through the fluid.
Direct current voltage is supplied – the
higher the voltage, the quicker the
sample moves.
DNA Fingerprinting Process
1.
2.
3.
4.
5.
Tissue Used: blood, hair follicles, semen,
skin, saliva
Amplify sample: use a process called
PCR – polymerase chain reaction
Add restriction enzymes
Gel electrophoresis
Compare banding patterns