Selective breeding and genetic engineering

What is selective breeding?

Humans choosing parents with desirable characteristics and breeding them to produce offspring with those traits.

Give examples of selective breeding.

• Cows → high milk/meat yield.

• Crops → disease resistance.

• Dogs → temperament/appearance.

• Horses → speed/strength.

What are the disadvantages of selective breeding?

• Reduces genetic variation (inbreeding).

• Can cause inherited health problems (e.g. dog breeds).

• Reduced ability to adapt to environmental change/disease.

What is genetic engineering?

Directly modifying the genome of an organism by inserting a gene from another organism.

What are the steps in genetic engineering?

1. Desired gene is cut out with enzymes (restriction enzyme).

2. Gene is inserted into a vector (bacterial plasmid or virus).

3. Vector is used to insert gene into the target organism’s cells.

4. New organism shows the desired characteristic.

Give examples of genetic engineering.

• Bacteria genetically engineered to produce insulin.

• GM crops → disease/pest resistance, higher yield.

• Sheep modified to produce useful proteins in milk.

What are the advantages of GM crops?

Higher yield, disease resistance, better nutrition (e.g. Golden Rice with vitamin A).

What are the disadvantages of GM crops?

Concerns about long-term health effects, reduced biodiversity, possible spread of genes to wild plants.

How can plants be cloned?

• Cuttings → simple, cheap.

• Tissue culture → small group of cells grown into new plants in sterile conditions (used in research & preserving rare species).

What is embryo transplant cloning?

Splitting a developing embryo into several cells → each develops into a clone.

What is adult cell cloning?

• Nucleus removed from unfertilised egg.

• Nucleus from adult body cell inserted into egg.

• Electric shock stimulates egg to divide.

• Embryo implanted into surrogate mother.

What are the potential benefits of cloning?

Save endangered species, produce genetically identical animals with desirable traits, medical uses.

What are the risks of cloning?

Reduced variation, ethical concerns, health problems in clones.