B3-New Genes for Old

Selective Breeding

Animals or plants with favourable characteristics are selected and deliberately crossbred to produce offspring with the desired characteristics. This is selective breeding. These offspring can then also be selected and bred until the desired result is achieved. But it can take many,many generations to get the desired results.

Selective breeding can contribute to improved agricultural yields in animals and crops. For example:

• Quantity of milk- cows have been selectively bred to produce high volumes of milk daily.
• Quality of milk- Jersey cows have been selectively bred to produce rich and creamy milk.
• Beef production- Some cattle have been selectively bred for characteristics such as hardiness, early maturity and high numbers of offspring.

Selective breeding may lead to in-breeding, which can cause health issues within a species.

There are risks and disadvantages to selective breeding. Intensive selective breeding reduces the gene pool, and the number of different alleles in the population decreases so there is less variation. Lack of variation can lead to an accumulation of harmful recessive characteristics (in-breeding).

Genetic Engineering

All living organisms use the same basic genetic code (DNA), so, genes can be artificially transferred from one living organism to another. This process is called genetic engineering or genetic modification. The transfer of genes can produce organisms with different characteristics. 

Altering the genetic make-up of an organism can be done for many reasons:

• To improve crop resistance to frost damage, disease or herbicides, e.g. soya plants are genetically modified by inserting a gene that makes them resistant to  herbicide, so the plants can grow better without…