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1 markPatterns of Inheritance

CAPE Biology Unit 1 · 2008 · Paper 2 · Question 2(a)(ii)

Flower colour in certain plants is controlled by two genes. One gene codes for colour pigments in the petals, with alleles R (red) and r (white) being co-dominant. The other gene codes for an enzyme system that enables pigment production, with alleles C for active enzymes and c for inhibited enzymes. Homozygous recessive plants (cc) cannot synthesize pigment and produce white flowers. A plant with genotype RRCC is crossed with a double homozygous recessive plant.

State the phenotype of the F1 plant.

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Other parts of this question

  1. 2(a)(i)State the genotype of the F1 plant.[1 mark]
  2. 2(b)State the FOUR different combinations of the alleles carried in the gametes of this F1 dihybrid plant (plant produced in (a) above).[1 mark]
  3. 2(c)(i)Use the Punnett Square shown in Table 1 to show the genotypes of the F2 generation of this dihybrid cross.[2 marks]
  4. 2(c)(ii)Give the ratio of red : pink : white flowers.[3 marks]
  5. 2(d)Complete the Chi-squared calculation in Table 2 and the final Chi-squared sum using the formula provided.[4 marks]
  6. 2(e)(i)How did the students determine the degrees of freedom?[1 mark]
  7. 2(e)(ii)The students checked the 5% probability in order to determine whether the result was significant or insignificant. What was their decision, and why?[2 marks]
  8. 2(e)(iii)If the Chi-squared value had been 7.0, what information could have been gained concerning the results of the monohybrid cross experiment?[1 mark]

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