6 3 Anthocyanin is a purple pigment found in a range of vegetable plants. The photograph shows some carrots from a variety called Purple Haze. (a) Describe how you would investigate the effect of temperature on the permeability of the membranes in the root cells of these purple carrots. 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Turn over 7 (b) The anthocyanins in purple carrots are used as antioxidants in the food industry. Purple Haze carrots with a mass of 750g contain 1265.25 mg of anthocyanin. Calculate the percentage of anthocyanin in these carrots. Give your answer to two decimal places. (2) Answer .............................................................. (c) Purple cauliflower plants also contain anthocyanins. Cauliflowers can be light purple, dark purple or white. The photograph shows a dark purple cauliflower. 8 The colour in cauliflowers is controlled by a single gene with two alleles. Purple colour is controlled by the allele Pr. White colour is controlled by the allele pr. In an investigation, dark purple cauliflowers were crossed with pure bred white cauliflowers. The F1 generation cauliflowers were all light purple in colour. (i) State the genotype of the F1 generation. (1) .................................................................................................................................................................................................................................................................................... (ii) The F1 generation was then self‑fertilised to produce the F2 generation. The numbers observed (O) in the F2 generation were: 31 white cauliflowers, 52 light purple and 20 dark purple cauliflowers. It was concluded that the purple colour in cauliflowers is controlled by a single gene with two codominant alleles. State the expected (E) number of each of the three phenotypes in the F2 generation. (2) .................................................................................................................................................................................................................................................................................... .................................................................................................................................................................................................................................................................................... (iii) Calculate the value for Chi squared using these results. Use the formula for Chi squared: − = ∑ χ 2 2 ( ) O E E (3) Answer .............................................................. Turn over 9 (iv) The table shows some critical values for Chi squared. Degrees of freedom p value 0.900 0.500 0.100 0.050 0.010 1 0.016 0.455 2.706 3.841 6.635 2 0.211 1.386 4.605 5.991 9.210 3 0.584 2.366 6.251 7.815 11.345 4 1.064 3.357 7.779 9.488 13.277 Explain why the conclusion that colour in cauliflowers is controlled by a single gene with two codominant alleles is likely to be valid. 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(Total for Question 3 = 16 marks)