Modern Dairy Cattle:- produce 25liters of milk a day as a result of artificial selection. Farmers select females with high milk yields and males whose mothers have high milk yields to breed together. They then select the offspring with the highest milk yield to breed them together
Bread Wheat:- (Triticium aestivium) is used to produce flour for bread making. Farmers select plants with high yields (big ears) and breed them. They select the offspring with highest yeild and breed together.
Triticium aestivuim is an allopolyploid produced from 2 separate hybridisations followed by chromosome doubling in the new hybrid. The initial hybridisation occured 10,000 years ago. Modern wheat has 42 chromosomes, that is, six complete genomes each of 7 chromosomes so produces a higher yield
Problems: Future generations will share very similar genes and this could mean
- Diseases are more dangerous as all the organisms would be affected
- Increased risk of genetic disease caused by recessive genes
- Inbreeding leads a reducing in the size of the gene pool, making in more difficult to produce new varieties in future