Explain why rice has been genetically modified so it produces extra $\beta$ carotene.
The earliest forms of Golden Rice™ produced only a very small mass of β carotene per gram of rice. Research then continued in an attempt to increase this. Fig. 4.1 shows the metabolic pathway by which β carotene is synthesised in plants, together with the enzymes that catalyse each step of the pathway.
Investigations were done to find out whether psy genes from species other than daffodils would enable rice endosperm to produce larger amounts of β carotene than the earliest forms of Golden Rice™. The findings are shown in Table 4.1.
Name the type of enzyme that would have been used to cut the psy gene out of the DNA of the plant cells.
Explain why a promoter had to be inserted into the plasmids.
Explain whether or not these results support the hypothesis that the psy gene, not the crtI gene, was limiting the production of β carotene in genetically modified rice.
The original reason for choosing a psy gene from daffodils was that daffodils produce large amounts of β carotene in their yellow petals, and because they are monocotyledonous plants, like rice. Suggest explanations for the much lower production of β carotene in rice containing the psy gene from daffodils than in rice containing the psy gene from maize.
Describe the possible drawbacks of growing Golden Rice™.