Applied Genetics

Selective Breeding and Genetic Engineering

Selective Breeding• = crossing of plants or animals that

have desirable traits to produce offspring with those traits

• Increased strength• Leaner meat (less fat)• Disease resistance• Larger grain/fruit• Better taste

hybridization

• = crossing two organisms (same genus/species, “kind”) with variations of particular trait(s) to produce offspring with a mixture of the trait(s)

• Offspring inherits traits of both parents

• Donkey X horse = mule

• Modern grains – corn, wheat

• Ancient wild wheat X wild goat grass = nutritious hybrid wheat used for bread

• The greater the difference between “kinds” (genus/species) being hybridized, the more likely the hybrid will be sterile

Inbreeding

• = crossing 2 organisms that have the same or similar trait(s) to produce animals with the same trait(s)

• Idea is to preserve the desirable traits

• Organisms are genetically similar and can lead to negative consequences:

• Increased chances of inheriting disorders

• Increased chances of contracting certain diseases

• Decreased ability to adapt to environmental changes

•

•

Weird hybrids liger = cross between lion

(father) and tiger (mother)

Weird hybrids• Tigon = cross between male tiger and

female lion

• Beefalo/cattalo = bison x cow

• Hinny

• Female donkey x male horse

Cama = male camel x female llama

Genetic Engineering

• Process in which genes (sections of DNA) are taken from one organism and transferred to another

Recombinant DNA

• Section of DNA is separated from strand of one organism

• This is spliced into the DNA of another organism

• DNA is now combined

• Modified DNA will cause cells to carryout processes in a different way

Products resulting from genetic engineering

• Medicine

Insulin, human growth hormone (produced by altered bacteria)

Hepatitis B vaccine (produced by altered yeast cells)

• Genetically Modified Organisms (GMO)

• Genetically Engineered Organisms (GEO)

Transgenic cropsGM foodsTransgenic animals• Much of these are used in

agriculture

transgenic goats

(spider genes for web silk protein)

(Nexia Biotechnologies)

Used to manufacture BioSteel® & Protexia™

Agricultural uses• Herbicide-tolerant crops

• Insecticidal crops

• Better taste, texture, longer shelf-life, larger size, better suited for mechanical harvesting

Potential problems

• Cross-pollination of GM crops to wild varieties can cause weeds to become herbicide resistant

• Insects may become quickly resistant to insecticides because of exposure to GM crops

• Predators that eat insects who have

eaten GM crops can be affected in unknown ways

• People who eat GM crops can be affected in unknown ways

Toxic effectsPathogenic effectsAllergic reactionsResistance to antibiotics

Terminator genes

• Plants have been developed that have a trait that kills developing embryos in seeds so that seeds from crops cannot be saved & planted the following season

Warnings

• Genes are now known to control more than one trait

• By altering/changing a single gene, multiple traits may be changed in ways we can’t predict

• Human genes are only a small percentage of the information contained in DNA (5% or less)…we don’t know what most of the rest does

• Humans have only 300 more genes than what are also found in mice…

• “This tells me genes can’t possibly explain all of what makes us what we are.”

Craig Venter, president of Celera Genomics (Maryland firm that led one of the mapping teams for the Human Genome Project)

The Future….

• Chimera – organism or component composed of different genetic material

• So far…• Pigs with human blood• Mice with human brain cells• Sheep with human tissues in

hearts & livers• Fusion of human & rabbit bio-

matter produced chimeric embryos