Advances in Genetics
Methods of Developing Organisms
With Desirable Traits
• Selective Breeding
• Cloning
• Genetic Engineering
Selective Breeding
• The process of selecting a
few organisms with desirable
traits to serve as parents of
the next generation.
• Used for thousands of years
with various plants and
animals.
• Types
• Inbreeding
• Hybridization
Inbreeding
• Two individuals that have identical or similar sets of alleles
are crossed.
• Resulting organisms are very similar to their parents.
• Used to produce breeds of animals with specific traits
• Ex. Purebred Lab retrievers, German shepherds
• Increases probability that organisms may inherit alleles that
lead to genetic disorders.
• Ex. Hip problems in many breeds of dogs
Hybridization
• Two genetically different individuals are crossed
• Organism is bred to have the best traits from
both parents
• Ex. Corn with many kernels crossed with
disease-resistant corn
• Most crops grown on farms and in gardens are
hybrids.
Cloning
• Although selective breeding does not
allow the breeder to control whether the
desired allele will be passed or not,
cloning does.
• Clone
• Organism that is genetically identical to the
organism from which it was produced.
• Cloning Plants
• Small part is cut from plant and regrows into
a genetically identical plant.
Cloning in Plants
Cloning Animals
• Dolly the Sheep
• Removed egg cell from one sheep
• Nucleus in egg cell replaced with nucleus from a sixyear old sheep
• Egg implanted into uterus of 3rd sheep
• Dolly born 5 months later, genetically identical to the
six-year old sheep
Genetic Engineering
• Genes from one organism are transferred into
the DNA of another organism.
• Called “Gene Splicing”
• DNA molecule cut open
• Gene from another organism is spliced into it
• Used to
• Produce medicine
• Improve food crops
• Try to cure human genetic disorders
Genetic Engineering in Bacteria
• Bacteria used because they reproduce
rapidly.
• Insulin gene spliced into bacteria- (into the
plasmid)- so that the bacteria will produce
insulin.
Genetic Engineering in Bacteria
Genetic Engineering in Other
Organisms
• Used in plants and other animals.
• Ex. Human clotting gene inserted into cows.
Cows then produce clotting protein in milk, which
can then be extracted for humans.
Gene Therapy
• Working copies of a gene inserted directly into
cells of a person with a genetic disorder
• Used to correct some genetic disorders
Genetic Engineering
DNA Fingerprinting
• DNA pattern is unique for each individual
• Used often in crime investigations
Human Genome Project
• Identified the DNA sequence of every gene in
the human genome.
• Involves nearly 25,000 genes
• May lead to new treatments and prevention
strategies for many genetic disorders and for
diseases such as cancer.
Summary Questions
• Name three techniques that people have used to
produce organisms with desired traits.
• Why do scientists want to identify the DNA
sequence of every human gene?
• What is genetic engineering? Describe three
possible benefits of this technique.
• Explain how a DNA fingerprint is produced.
What information can a DNA fingerprint reveal?