Selective Breeding• Over 1000’s of years mankind has grown plants and

domesticated animals.

• Characteristics have been selected for repeated breeding

• e.g - milk yield in cattle

• - meat yield in poultry and cattle

• - woolly fleece in sheep

• - corn seeds with high oil or protein content

• Only members of a species with the required characteristic are allowed to breed

Genetic Engineering - Bacterium

• Each cell has a complete chromosome and a plasmid

• Plasmid and chromosomes are made of genes

• Each gene makes up one protein (e.g enzyme - which then controls one specific reaction)

• Cell activity depends upon chromosomes

• e.g. One gene could make lactase to help bacteria break down lactose

Genetic Engineering

• Transfer of pieces of chromosomes from one organism to another

• e.g. human to bacterium

• Reprogrammed cell becomes a factory for the required product e.g insulin

• Several stages involved

Advantages of using reprogrammed bacteria

• By transferring a piece of chromosome, the organism receiving the material is being manipulated

• Advantages: Much easier (& cheaper) to mass produce bacteria cells, than to clone and mass produce complex organisms e.g. humans

• Mass quantities of a useful product e.g insulin can be produced

Genetic Engineering v Selective Breeding

• Both can alter the genetic makeup of a species for scientific benefit

• Selective Breeding

• Requires years of careful selection & breeding

• Doesn’t always produce the ideal organism

• Only animals that would normally produce the required product can be used

Benefits of Genetic Engineering

• Allows scientists to directly alter the genotype of a species by manipulating it’s chromosomes

• Altered organism has a new genotype suited to mankind’s needs

• Allows for a species to be programmed to make products previously only made by another species

• E.g. bacteria producing human insulin

Applications of Genetic Engineering

• Medical - copy table 10.2 on pg. 208• Commercial -• - Bacteria can be used in detergents to digest

stains, or to make antifreeze (ethylene glycol)• - Yeast for beer making can be modified to

produce more alcohol, but fewer carbs• - Cheese making: rennin curdles milk, normally

from calf stomach linings. Can now be produced by yeast cells

Transgenic multicellular organisms

• Genetic engineering on more complex organisms• Agrobacterium tumefaciens - soil bacterium that

injects a plasmid into plant tissue (‘natural genetic engineer’)

• Genetic material from plasmid is incorporated into the plants DNA. Plant expresses bacterial genes

• Scientists have altered the plasmids so the bacterium inserts useful genes into the plant DNA

• These are Transgenic plants

Transgenic Plants

• Plants that have gained new genetic material from foreign DNA

• At present the benefits to certain plants have included

• extended shelf life in apples & tomatoes, resistance to weedkiller in soya crops, pea plants that produce their own insecticide

Transgenic organisms - future

• Cereals : hoped that in future cereal crops will be modified to contain genes for certain characteristics

• e.g resistance to herbicides, drought, pests, micro-organisms & salinity/ increased photsynthetic rate

• Future - animal genes into plants e.g already haemoglobin grown in tobacco plants