Genetic EngineeringChapter 13 (Sections 1, 2 and 4)

13-1: Changing the Living World

• What is the purpose of selective breeding?

• Why might breeders try to induce mutations?

Selective Breeding• Selective breeding is allowing animals with

desired characteristics to produce the next generation– Humans use selective breeding to pass desired traits

on to the next generation of organisms

• Hybridization is the crossing of two dissimilar organisms to bring together the best of both

• Inbreeding is the continued breeding of individuals with similar characteristics and backgrounds

• http://worldmysteries9.blogspot.com/2010/01/top-10-hybrid-animals.html

Selective breeding has been used for thousands of years to produce better crops

Hybridization can be used to combine useful characteristics from different organismsFor Example: Horse + Donkey = Mule

Crossing a male lion and a female tiger produces a liger.(Reverse the sexes and you get a Tigon)

Inbreeding can be used to maintain desired characteristics

                     

Increasing Variation

• Breeders can increase the genetic variation in a population by inducing mutations (the ultimate source of variability)

• Breeders increase the mutation rate with radiation or chemicals

• Scientists have been able to develop useful strains of bacteria, and produce polyploidy (many sets of chromosomes) in plants (stronger and larger plants)

Polyploidy results in larger fruits, flowers, and plants

13-2: Manipulating DNA

• Scientists use their knowledge of the structure of DNA and its chemical properties to study and change DNA molecules

• Different techniques are used to extract DNA from cells, to cut DNA into smaller pieces, to identify the sequence of bases in a DNA molecule, and to make unlimited copies of DNA

The Tools of Molecular Biology

• Genetic engineering is making changes to the DNA code of a living organism

The Tools of Molecular Biology

• Cutting DNA: Restriction enzymes cut DNA at specific sequences of nucleotides

• PCR – Polymerase Chain Reaction can make multiple copies of the cut sequence

The restriction enzyme EcoR I, for example, finds the sequence CTTAAG on DNA. Then, the enzyme cuts the molecule at each occurrence of CTTAAG.

The cut ends are called sticky ends because they may “stick” to complementary base sequences by means of hydrogen bonds.

The Tools of Molecular Biology

• DNA extraction: Cells are opened and the DNA is separated from other cell parts

The Tools of Molecular Biology

• Separating DNA: Gel electrophoresis separates pieces of DNA based on their size– Used to compare genomes or locate genes

– http://www.youtube.com/watch?v=drC7rR7CIBg&feature=fvw

* Using the DNA Sequence *

• Once DNA is in a manageable form, its sequence can be read, studied, and even changed

• Knowing the sequence of an organisms DNA allows researchers to:– Study specific genes– Compare genes from different organisms– Discover the function of different genes and gene

combinations

* Using the DNA Sequence *

• Recombinant DNA makes it possible to take a gene from one organism and attach it to the DNA of another organism

• Polymerase Chain Reaction (PCR) is used to make copies of a particular gene

• http://www.pleasanton.k12.ca.us/avhsweb/thiel/bio/labs/csi.html

• PCR permits early diagnosis of malignant diseases such as leukemia and lymphomas, which is currently the highest developed in cancer research and is already being used routinely

• http://learn.genetics.utah.edu/content/labs/pcr/

13-4: App. of Genetic Engineering

• Genetic engineering makes it possible to transfer DNA sequences, including whole genes, from one organism to another

• Luciferase an enzyme that allows fireflies to glow, has been inserted into tobacco plants, causing them to glow in the dark

Bioengineers have also developed salmon that grow to market weight in about half the typical time, disease-resistant cows and catfish needing fewer antibiotics, and goats whose milk might help ward off infections in children who drink it.

This little piggy’s manure causes less pollution. This little piggy produces extra milk for her babies. And this little piggy makes fatty acids normally found in fish, so that eating its bacon might actually be good for you.

•The Department of Agriculture's Agricultural Research Service genetically engineered the cow at left to produce an antimicrobial protein to resist infection with Staphylococcus aureus

•Researchers at the University of Missouri-Columbia genetically engineered the pig at right to serve as a model of cystic fibrosis in humans.

Transgenic Organisms• Transgenic organisms have genes from other species• Because they reproduce rapidly and are easy to grow,

transgenic bacteria now produce many important substances for health and industry– insulin, growth hormone, clotting factor, etc

• Transgenic animals have been used to study genes and improve the food supply– Mice with human immune systems, livestock with extra growth

hormone genes

• Transgenic plants can produce natural insecticides, or resist weed-killing chemicals

•GTC Biotherapeutics created the transgenic goat at right as part of a project with researchers at the University of Pennsylvania to refine strategies for genetic engineering

Cloning

Cloning• A clone is a member of a population of

genetically identical cells produced from a single cell

• Dolly the sheep was cloned by – (1) removing the nucleus of an egg cell– (2) inserting the nucleus from an adult cell– (3) placing the embryo into a foster mother to

develop

• Cows, pigs, mice and other mammals have been produced

• Cloning humans is scientifically possible, but raises serious ethical and moral issues

Therapeutic cloning

• also called "embryo cloning," is intended for medical use

• The embryonic stem cells that this type of cloning produces can be used to create skin for burn victims, organs for transplant patients, or cells for those with spinal cord injuries.