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3 marksPatterns of Inheritance

CAPE Biology Unit 1 · 2018 · Paper 2 · Question 2(a)(ii)

Seed type in pea plants is determined by a single gene with round seed, R, dominant to wrinkled seed, r. Three pairs of homologous chromosomes are depicted in Figure 2, with the gene locus for seed type indicated by X. The characteristics are: A - homozygous round-seeded variety, B - homozygous wrinkle-seeded variety, C - heterozygous variety.

Draw a Punnett square in the following box to illustrate a test cross involving a pea variety which is heterozygous for seed type. State the ratio of the phenotypes for the offspring.

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Other parts of this question

  1. 2(a)(i)In Figure 2, insert the appropriate alleles which correspond to the phenotypes of A, B and C given the following characteristics:[3 marks]
  2. 2(a)(iii)Distinguish between 'a gene' and 'an allele'.[2 marks]
  3. 2(b)(i)Make a scaled drawing of the cells labelled D, E and F in Figure 3. Show the magnification of the drawing.[4 marks]
  4. 2(b)(ii)Identify the cell cycle stages displayed in cells D, E and F in Figure 3.[3 marks]

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