Plant and animals are bred to improve characteristics to help support sustainable food production.

Breeders develop crops and animals with

• higher food yields
• higher nutritional values
• pest and disease resistance
• the ability to thrive in particular environmental conditions

Plant field trials are carried out in a range of environments to compare the performance of different cultivars or treatments and to evaluate GM crops.

In designing field trials account has to be taken of

• the selection of treatments → to ensure valid comparisons
• the number of replicates → to take account of the variability within the sample
• the randomisation of treatments → to eliminate bias when measuring treatment effects

In inbreeding, selected related plants or animals are bred for several generations until the population breeds true to the desired type due to the elimination of heterozygotes.

Analysis of patterns of inheritance in inbreeding using monohybrid crosses.

A result of inbreeding can be

• → An increase in the frequency of individuals who are homozygous for recessive deleterious alleles.

  → These individuals will do less well at surviving to reproduce.

  → This results in inbreeding depression.

New alleles can be introduced to plant and animal lines by crossing a cultivar or breed with an individual with a different, desired genotype.

In animals, individuals from different breeds may produce a new crossbreed population with improved characteristics. The two parent breeds used to produce a crossbreed can be maintained to produce more crossbred animals showing the improved characteristic.