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 six-

year 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 so that they 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 60,000-80,000 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?