Unit 3 Key Area 2

Question 1

Why might a plant or animal breeder breed particular individuals?

Answer 1

To help improve certain characteristics, or to help support sustainable food production

Question 2

What might be some of the characteristics that breeders of plants or animals select for?

Answer 2

• Increased nutritional value
• Increased food yields
• Increased resistance to pests or disease
• the ability to thrive in particular environmental conditions

Question 3

Suggest some of the reasons why a field trial might be carried out?

Answer 3

Field trials are carried out to
- evaluate the performance of different cultivars
- evaluate different GM crops

Question 4

What are the factors that must be taken into account when designing field trials?

Answer 4

• Selection of treatments
• number of replicates
• randomisation of treatments

Question 5

Why must selection of treatments be taken into account when designing a field trial?

Answer 5

Selection of treatment ensures valid results are drawn from the field trial

Question 6

Why must number of replicates be taken into account when designing a field trial?

Answer 6

To take into account the variability of results within the sample

Question 7

Why must randomisation of treatments be carried out when designing a field trial?

Answer 7

To eliminate bias when measuring treatment effects

Question 8

Describe the process of inbreeding?

Answer 8

selected individuals of related plants or animals are bred together for several generations until the population breeds true to the desired type. Due to the elimination of heterozygotes.

Question 9

What is meant by inbreeding depression?

Answer 9

Inbreeding depression is caused by excessive inbreeding where there is an increase in the frequency of individuals that are homozygous for a deleterious alleles. These individuals will not do well at surviving to reproduce due to the expressed deleterious characteristics.

Question 10

How can new alleles be introduced into plant and animal lines?

Answer 10

by crossing a cultivar with an individual of a different desired genotype (in plants)
by crossing a breed with an individual of a different desired genotype (in animals)
This practice is called crossbreeding

Question 11

Why are the F1 generations in naturally inbreeding plants or animals not bred together?

Answer 11

As the resulting F2 variation will display too much variation of the desired characteristic.

Question 12

What are some of the ways of genetically modifying plants to have increased pest resistance and herbicide tolerance?

Answer 12

• The BT toxin gene when inserted into plants causes increased pest resistance
• glyphosate gene gives the plant an increased tolerance for herbicides.