Genetic
Engineering
Chapter 15 in Textbook
Selective Breeding
• Selective Breeding: allowing only those organisms with
desired characteristics to reproduce.
– How could you use selective breeding to develop dogs
with more intelligence?
– Selective breeding takes advantage
of natural genetic variation (the
trait must already exist in the
population)
Selective Breeding
2 Methods of selective breeding
1. Hybridization: crossing dissimilar individuals together
to get the best of both organisms
Ex: Killer Bees – While attempting to create a bee that
produces more honey in tropical climates scientist bred a
European honey bee with a African honey bee.
2. Inbreeding: the continued breeding of individuals
with similar characteristic
Ex: Purebred Dog Breeds – dog breeds are created by
breeding individuals with similar characteristics to ensure
that the combination of traits will be passed on to the next
generation.
Selective Breeding
• In order for selective breeding
to work, you need a wide
variation of genetic traits.
– Explain you cannot use
selective breeding to create
a monkey that glows in the
dark?
• How do new traits get introduced into a population?
– Induce mutations to develop new traits in a population
(Mutations are the ultimate source of genetic traits)
Selective Breeding
Limitations of selective breeding and mutations:
– Selective breeding requires traits already exists in a
population – we can not make new traits.
– Mutations are unpredictable and will not create the
exact traits that we want. (most mutations are harmful
to the organism)
Scientists are learning how to directly manipulate the DNA of
an organisms to produce desired traits.
• Genetic Engineering: the development and application
procedures, and technologies that allow you to directly
manipulate an organisms DNA
Gel Electrophoresis
Gel Electrophoresis: Method for separation and analysis of
macromolecules (DNA, RNA and proteins) and their
fragments, based on their size and charge
Gel Electrophoresis
Basic Steps for DNA Gel Electrophoresis
1. Mix a sample of DNA with a restriction enzyme.
• Restriction Enzymes: a protein that cuts DNA at a
specific nucleotide sequence.
• Different samples of DNA produce fragments of
different sizes.
Gel Electrophoresis
2. Separating the DNA fragments
– A mixture of DNA fragments is put into one end of a
porous gel
– An electric
current drives
the DNA through
the gel
– The smaller the
segment, the
faster it moves.
Gel Electrophoresis
3. Analyzing the Results
– Measure the distance
the segment of DNA
traveled away from the
original position.
– Smaller fragments of
DNA move further
across the gel.
– DNA always have a
negative charge, so it
moves towards the
positive electrode.
Recombinant DNA
Recombinant DNA: Molecule of
DNA that is created by joining
segments of DNA from different
sources.
How to create recombinant DNA:
1. Cut both 2 different samples of
DNA with the same restriction
enzyme.
–
Sticky Ends: Single stranded
DNA sequence created after the
DNA is cut by certain restriction
enzymes
Recombinant DNA
2. Join the 2 cut DNA segments
together.
– Since both of the DNA
molecules were cut with the
same restriction enzymes
the sticky ends will contain
complimentary bases.
– DNA ligase can be used to
fuse together the DNA
fragments.
– Beside recombinant DNA, in
what other process is DNA
ligase used?
Recombinant DNA
How is recombinant DNA useful?
Recombinant DNA can be inserted into bacterial cells to
create human growth hormone.
How to make bacteria with recombinant DNA:
1. Remove a plasmid for a
bacteria cell.
– Plasmid: A small, circular
DNA molecule in bacterial
cells that is separate from
the bacteria’s
chromosome.
Recombinant DNA
2. Cut the plasmid and the human DNA with the same
restriction enzyme.
3. Use ligase to join the fragment of human DNA containing
the insulin gene with the cut bacterial plasmid.
4. Insert the plasmid with recombinant DNA into a bacteria
cell.
Recombinant DNA
5. The bacteria cell divides and produces more transgenic
bacterial cells that will produce human insulin that can be
given to diabetes patients.
Transgenic Organisms: Organisms that have had genes
from other species inserted into their genome
Cloning
Clone: genetically identical individuals produced from a
single cell.
• Cloned colonies of bacteria and plants are easy to grow
How to clone a mammal:
1. Remove the nucleus from a diploid cell of the
animal you wish to clone.
The cloned lamb is identical to which
sheep?
Cloning
2. Remove the haploid nucleus of an unfertilized egg cell
and replace it with the diploid nucleus.
3. The diploid egg cell will begin to divide, growing into
an embryo.
4. The embryo is implanted into a foster mother where it
develops until birth.
The cloned lamb identical to which
sheep?
Ethics and Impacts of Genetic Engineering
Understand the pro and cons of each of the following:
1. Genetically Modified Foods (GMO’s)
2. Designer Babies
3. Cloning Mammals