3.2) Plant and Animal Breeding

Question 1

• How can plant and animal breeding be used?

Answer 1

• Plant and animal breeding are designed around improving characteristics to help support sustainable food production.

Question 2

• What is the importance of plant field trials and describe the features of how are they designed.

Answer 2

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

1. Selection of treatments used (VALIDITY - variables):
   ➞ to ensure valid comparisons where only one treatment must be trialled at one time.
2. Number of replicates (RELIABILITY - how many times)
   ➞ several replicates (minimum of 3) must be used to improve the reliability of results and to take account of variability within the sample.
3. Randomisation of treatments
   ➞ must be applied randomly to the test area to eliminate bias when measuring treatment effects.

Question 3

• Describe and explain inbreeding and the potential consequences.

Answer 3

• ‘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.
• However, a result of inbreeding can be an increase in the frequency of individuals who are homozygous for recessive deleterious alleles
  ➞ and will do less well at surviving and reproducing (inbreeding depression).

Question 4

• Describe and explain crossbreeding and the potential consequences.

Answer 4

• In ANIMALS
  ➞ individuals from different breeds may produce a new crossbred population with improved characteristics
  ↳ and can be maintained to produce more crossbred animals showing the improved characteristics.
• In PLANTS
  ➞ F¹ hybrids (produced by the crossing of two different inbred lines) create a relatively uniform heterozygous crop - with increased vigour and yield.
  ↳ However, F¹ hybrids are not usually bred together as F² produced shows too much variation.

Question 5

• Describe the role of genetic technology in plant and animal breeding programmes.

Answer 5

• As a result of genomic sequencing, organisms with desirable genes can be identified and then used in breeding programmes.
• Breeding programmes can involve crop plants that been genetically modified using Recombinant DNA technology.