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 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 Attach the DNA fragment to a carrier Transfer into the host organism

Recombinant DNA technology

Restriction enzyme action Click on image to play video.

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