3.2 - Plant & Animal Breeding Flashcards
Manipulating Heritable Characteristics
Breeders manipulate heritable characteristics to improve: plant crops, animal stock, and ensure that food production is sustainable.
Improvements:
* higher food yields
* higher nutritional values
* pest resistance
* disease resistance
* ability to thrive in particular environmental conditions
Plant Field Trials Are Carried Out To…
- compare different treatments in different environments
- evaluate GM crops
- compare different cultivators in different environments
Considerations When Planning Field Trials Include…
- Selection of treatments: only one factor is changed at a time so that a valid and fair comparison can be made
- Number of replicates: replicates need to be carried out so the results are reliable. Replicates also take account of variability within the sample.
- Randomisation of treatments: Bias is eliminated when measuring the effects of the treatment as the treatment is randomly chosen for different plots.
Inbreeding Definition
Offspring have two closely related parents from a smaller gene pool.
Heterozygosity
Having 2 different alleles for the same trait e.g. Aa
Homozygosity
Having 2 similar alleles for the same trait e.g. AA or aa
Inbreeding
Selected plants and animals with desired characteristics are bred for several generations until the resulting population only produce homozygous offspring for a chosen characteristic.
This homozygosity occurs through the elimination of heterozygosity. Pattern of inheritance can be analysed using monohybrid crosses.
Inbreeding Depression
Accumulation of recessive homozygous alleles that are deleterious (bad for the organisms health)
Cross-Breeding
Cross breeding uses individuals from different breeds to create a new population with improved characteristics.
New alleles can be introduced to plant and animal lines by crossing a cultivar (plant with desirable characteristics) or breed with an individual with a different, desired genotype.
Advantage of Cross-Breeding
- Produces individuals that sustain the population and avoids inbreeding depression
- Can produce more F1 at any time
Disadvantages of Cross-Breeding
- Process takes a lot of time.
- Parental breeds must be maintained.
F1 Hybrid Definition
Individual resulting from a cross between two inbred parents of the same species that are genetically different.
Cross-breeding and F1 Hybrids
F1 hybrids in plants are produced by the crossing of two different inbred lines to create a relatively uniform heterozygous crop.
F1 hybrids often have increased vigour and yield. Plants with increased vigour may have increased disease resistance or increased growth rate.
When inbreeding animals and plants, F1 hybrids are not usually bred together as the F2 produced show too much variation.
Genomic Technology
Genomic sequencing allows organisms with desirable genes to be identified and used in breeding programmes to add these genes into a new cultivar of crop or breed animal.
Breeding programmes can involve crop plants that have been genetically modified using
recombinant DNA technology
