Season Ordinary variety yield / t per ha GM variety yield / t per ha Insecticide sprayed on GM crop / kg per ha 1 7.2 9.4 0.5 2 6.8 9.1 0.6 3 7.5 9.8 0.4 A ...
Question 1 Report
| Season | Ordinary variety yield / t per ha | GM variety yield / t per ha | Insecticide sprayed on GM crop / kg per ha |
|---|---|---|---|
| 1 | 7.2 | 9.4 | 0.5 |
| 2 | 6.8 | 9.1 | 0.6 |
| 3 | 7.5 | 9.8 | 0.4 |
A farmer compares an ordinary variety of maize with a genetically modified variety that contains a gene from a soil bacterium. This gene makes the maize produce a protein that is toxic to insect pests but harmless to the crop itself. Table 2.1 shows the mean crop yield and the mass of insecticide sprayed on each variety over three growing seasons on the same farm.
| Season | Ordinary variety yield / t per ha | GM variety yield / t per ha | Insecticide sprayed on GM crop / kg per ha |
|---|---|---|---|
| 1 | 7.2 | 9.4 | 0.5 |
| 2 | 6.8 | 9.1 | 0.6 |
| 3 | 7.5 | 9.8 | 0.4 |
(a) State what is meant by a genetically modified organism. [1]
(b) Calculate the mean yield of the genetically modified variety across the three seasons. [2]
(c) Using Table 2.1, describe two differences between the ordinary variety and the GM variety. [2]
(d) Explain how the gene from the soil bacterium increases the yield of the maize crop. [4]
(e) Suggest two possible disadvantages of growing this genetically modified crop. [4]
(f) State the name of the process used to insert the bacterial gene into the maize cells. [1]
Answer Details
This question is about genetic modification, using a Bt maize example and yield data.
(a) A genetically modified organism is one whose genes / DNA have been changed, for example by adding a gene from another organism [1].
(b) Mean yield of the GM variety across the three seasons:
\[ \frac{9.4 + 9.1 + 9.8}{3} = \frac{28.3}{3} = 9.43 \text{ t/ha} \]
So the mean yield is 9.43 t/ha (accept 9.4) [2; 1 for correct method, 1 for the answer].
(c) Any two differences from the table [1 each]: the GM variety has a higher yield in every season (about 9.1 to 9.8 t/ha compared with 6.8 to 7.5 t/ha); and the GM crop needs / uses only a small amount of insecticide (about 0.4 to 0.6 kg/ha).
(d) The bacterial gene increases yield because it makes the maize produce a (Bt) protein / toxin [1]; this toxin kills the insect pests that feed on the crop [1]; so less of the leaf and crop is eaten or damaged [1]; leaving more healthy leaf for photosynthesis and more grain surviving to harvest [1].
(e) Any two disadvantages, developed for the 4 marks [2 marks each, max 4]: loss of biodiversity / harm to non-pest (beneficial) insects such as pollinators [1][1]; pests may become resistant to the toxin over time, making it useless [1][1]; the GM seed is expensive and farmers become dependent on the company that sells it [1][1]; possible unknown effects on human health, or the escape / spread of the gene to wild plants [1][1].
(f) The process used to insert the bacterial gene into the maize cells is genetic engineering (genetic modification) [1].
Exam tip: when a calculated mean does not divide exactly, quote it to the same precision as the data (one decimal place here) and show the sum over the number of values for the method mark.
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