Genetic technology
Unit 4
Chapter 13
Selective Breeding
 Choosing plants and animals with the most
desired traits to be parents of the next
generation
 Increases amount of desired genes in a
population
 Inbreeding is mating between closely related
individuals and ensures pure lines.
 Overtime, inbreeding is detrimental because of
deleterious recessive genes.
Selective breeding common in dogs
and horses.
Hybrid vigor
 A hybrid is the offspring
of parents that have
different forms of a trait.
 Hybrids produced by
crossing two purebred
plants are often larger
and stronger than their
parents.
 Plants are often
hybrids.
Test cross
 a method of breeding dominant phenotype
individual to homozygous recessive individual
to determine the dominant individual’s
genotype

If the organism being tested is heterozygous, the
expected 1:1 phenotypic ratio will be observed.
Genetic engineering
 and more reliable method for increasing the
frequency of a specific allele in a population
 Recombinant DNA technology: cutting
(cleaving) DNA from one organism into small
fragments and inserting the fragments into a
host organism of the same or a different
species
Transgenic organisms
 Plants and animals that contain functional
recombinant DNA from an organism of a
different genus are known as transgenic
organisms because they contain foreign
DNA.
Steps for recombining DNA
1. Isolate the foreign DNA fragment that will be
inserted using restriction enzymes

bacterial proteins that have the ability to cut both
strands of the DNA molecule at a specific nucleotide
sequence called palindromes
2. Attach the DNA fragment to a carrier
3. Transfer into the host organism
Recombinant DNA technology
Restriction enzyme action
Click on image to play video.
Vector
 Mechanical or biological way for DNA from
one species to be carried into a host cell
Click on image to play video.
Gene cloning
 After foreign DNA has been inserted into a
plasmid, the recombined DNA is transferred
into a bacterial cell.
 Advantage: Bacteria reproduce quickly and
can produce millions of copies of the
recombinant DNA.
 Each identical recombinant DNA molecule is
called a gene clone.
Gene cloning using plasmid vectors
Cloned animal – Dolly the sheep
Polymerase chain reaction
 Method to copy DNA outside of a living
organism host
 Heat, enzymes, and nucleotides are mixed in
a machine to make multiple DNA copies.
Sequencing DNA
 Machines in laboratories can determine the
nucleotide order of small DNA fragments.
 The DNA sequence can be visualized using
gel electrophoresis techniques.
The entire human genome has been
sequenced.
 In 1990, scientists in the United States
organized the Human Genome Project
(HGP). It is an international effort to
completely map and sequence the human
genome, the approximately 35 000-40 000
genes on the 46 human chromosomes.
 In February of 2001, the HGP published its
working draft of the 3 billion base pairs of
DNA in most human cells.
 The sequence of chromosomes 21 and 22
was finished by May 2000.
Gel electrophoresis
 DNA cut with restriction
enzymes are loaded
into a gel.
 Electric currents
separate the DNA
fragments.
 DNA from two sources
can be compared for
similarities.
Loading gel
Applying electric field to separate
DNA
Comparing DNA fragments for
similarities
DNA fingerprinting
 DNA fingerprinting can
be used to convict or
acquit individuals of
criminal offenses
because every person
is genetically unique
Recombinant DNA technology in
society
 Scientists have
modified the bacterium
E. coli to produce the
expensive indigo dye
that is used to color
denim blue jeans.
 Pharmaceutical
companies already are
producing molecules
made by recombinant
DNA to treat human
diseases
Recombinant technology in society
 Recombinant bacteria are used in the production of
human growth hormone to treat pituitary dwarfism.
 Also, the human gene for insulin is inserted into a
bacterial plasmid by genetic engineering techniques.
Recombinant bacteria produce large quantities of
insulin
 Scientists can study diseases and the role specific
genes play in an organism by using transgenic
animals
 Crops have been developed that are better tasting,
stay fresh longer, and are protected from disease and
insect infestations
Gene therapy
 Gene therapy is the insertion of normal genes into
human cells to correct genetic disorders