key area 3.3 - plant and animal breeding

Question 1

desirable features for breeding programmes

Answer 1

• higher yields
• higher nutritional values
• resistance to disease and pests
• ability to grow and thrive in particular environmental conditions

Question 2

cultivar

Answer 2

• a variety of plant obtained by natural selection and or genetic manipulation and maintained by cultivation

Question 3

why carry out a plant field trial

Answer 3

• enables comparison of performance of different cultivars or treatments and to evaluate GM crops
• often carried out in a range of environments

Question 4

designing a field trial

Answer 4

• selection of treatments to be used
• number of replicates
• randomisation of treatments

Question 5

selection of treatments in a field trial

Answer 5

• allows for a fair comparison between treatment as long as no other factors are varied

Question 6

number of replicates in a field trial

Answer 6

• must have several replicates to take account for variability within samples and reduce experimental error
• more reliable results

Question 7

randomisation of treatments in a field trial

Answer 7

• randomising the pattern of replicates treatments eliminates a bias that could exist if plots were treated in an orderly sequence

Question 8

inbreeding

Answer 8

• the fusion of two gametes from close relatives over many generations unit a population breeds true to the desired type/characteristics due to the elimination of heterozygotes

Question 9

inbreeding depression

Answer 9

• forcing natural outbreeders to inbreed increases the frequency of individuals homozygous for recessive deleterious alleles
• this results in individuals struggling to survive and reproduce

Question 10

crossbreeding

Answer 10

• individuals from different breeds reproduce to try and produce offspring with improved characteristics

Question 11

outbreeding

Answer 11

• the fusion of two gametes from unrelated members for the same species

Question 12

F1 hybrid

Answer 12

• different inbred lines can be crossed to produce a relatively heterozygous crop
• these plants will show increased vigour leading to higher yield and resistance to disease

Question 13

why are F2 hybrids uncommon

Answer 13

• they show too much variation and lack desired characteristics

Question 14

genetic technology

Answer 14

• genome sequencing has resulted in the identification of desirable genes in organisms which can then be used in breeding programmes
• genes inserted into genomes of crop plants using recombinant DNA technology thus creating GM crops with improved characteristics
• eg Bt toxin gene and glyphosphate resistance gene