CHAPTER 6, SECTION 3: ADVANCES IN GENETICSScience 7

6-3 OBJECTIVES Describe three ways of producing organisms

with desired traits. Identify two applications of DNA technology

in human genetics.

SELECTIVE BREEDING Selective breeding, cloning, and genetic

engineering are three methods for developing organisms with desirable traits.

The process of selecting organisms with desired traits to be parents of the next generation is called selective breeding.

People have used selective breeding with many different plants and animals.

Inbreeding and hybridization are two types of selective breeding methods.

INBREEDING The technique of inbreeding involves

crossing two individuals that have similar characteristics.

For example, suppose a male and a female turkey are both plump and grow quickly. Their offspring will probably have those desirable qualities.

In bred organisms are genetically very similar and therefore inbreeding increases the probability that organisms may inherit alleles that lead to genetic disorders (example: hip problems in dogs).

HYBRIDIZATION In hybridization, breeders cross two

genetically different individuals. The hybrid organism that results is bred to

have the best traits from both parents. For example: a farmer might cross corn that

produces many kernels with corn that is resistant to disease so the offspring with have both traits.

CLONING A clone is an organism that has exactly the

same genes as the organism from which it was produced.

Researchers have cloned plants and animals such as sheep, dogs and pigs.

GENETIC ENGINEERING In genetic engineering, genes from one

organism are transferred into the DNA of another organism.

Genetic engineering can produce medicines and improve food crops.

BACTERIA AND GENETIC ENGINEERING Bacteria have been

genetically engineered to produce human insulin.

Insulin is needed for injections to treat people with diabetes.

Bacteria have human insulin producing genes inserted into their DNA to manipulate them into producing the insulin.

GENETIC ENGINEERING IN OTHER ANIMALS Human genes can be inserted into the DNA

of cows so that the cows produce the protein responsible for blood clotting in their milk. The protein is then extracted and used to treat hemophiliacs.

Genes have also been inserted into plant DNA which enables plants to survive in cold temperatures or in poor soil. Some genetically engineered plants can even resist pests.

GENE THERAPY Someday it may be possible to use genetic

engineering to correct some genetic disorders in humans.

Gene therapy will involve inserting copies of a gene directly into a person’s cells.

For example, doctors may be able to cure a person with hemophilia by replacing the defective allele on the X chromosome

CONCERNS ABOUT GENETIC ENGINEERING Some people are concerned about the long

term effects of genetic engineering. Some people worry that genetically

engineered crops may not be entirely safe. They fear that these crops might harm the environment or cause health problems in humans.

Scientists are studying these concerns to learn about the effects of genetic engineering.

LEARNING ABOUT HUMAN GENETICS Applications of DNA technology include

studying the human genome in detail and identifying people.

HUMAN GENOME PROJECT A genome is all the DNA in one cell of an

organism. The main goal of the Human Genome Project

has been to identify the DNA sequence of every gene in the human genome.

DNA of humans contain at least 30,000 genes and the average gene has 3,000 bases.

DNA FINGERPRINTING DNA technology can identify people and

show whether people are related.