There are many different strains of the soil bacterium Bacillus thuringiensis. It produces slightly different types of Cry-proteins, which are toxic to insects. Some types of cotton, known as Bt cotton, have been genetically modified to produce one of these proteins, Cry1Ac. This protein acts specifically to kill the larvae of butterflies and moths, including the cotton bollworm, Helicoverpa zea, a serious pest of cotton crops. The genetically modified cotton contains a 'genetic package' that includes: • the gene coding for Cry1Ac, the Bt protein • a promoter • a herbicide resistance gene that is used as a marker. (a) (i) Suggest the advantages of using, in Bt cotton, the gene coding for Cry1Ac, rather than one of the genes coding for other types of the Cry-protein. (ii) Explain why a promoter is included in the genetic package. (iii) Suggest how the herbicide resistance gene can be used as a genetic marker. (b) [Table 4.1] shows information about the cultivation of Bt cotton and non-GM cotton by farmers in India in 2002–2003. (i) With reference to Table 4.1, compare the costs involved in growing Bt cotton with the costs involved in growing non-GM cotton. (ii) Table 4.1 shows that farmers who grow Bt cotton have a higher net income than those who grow non-GM cotton. Use the information in the table to suggest one reason why some farmers in India choose to grow non-GM cotton, rather than Bt cotton. (c) In one region of India, Andhra Pradesh, a severe drought in 2002–2003 meant that Bt cotton grew less well than other varieties of cotton that were better adapted for the conditions. Suggest how a variety of Bt cotton that is better adapted to dry conditions could be produced from the existing varieties of Bt cotton, without using gene technology.