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Patterns of inheritance

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Question 21

In primroses (PrimulasinensisPrimula sinensisPrimulasinensis), flower colour is controlled by two genes, D/dD/dD/d and B/bB/bB/b.

  • The dominant allele, DDD, suppresses the synthesis of anthocyanin pigment, resulting in white flowers.
  • The recessive allele, ddd, allows pigment synthesis to occur so the flowers develop colour.
  • The dominant allele, BBB, controls the production of blue pigment.
  • Primrose plants homozygous for the recessive allele, bbb, produce red pigment (in the absence of the dominant inhibiting allele).

A white-flowered primrose plant was cross-pollinated with a blue-flowered primrose plant. All resulting offspring had the genotype DdBbDdBbDdBb.

a.

Identify the following:

  • The genotype of the white-flowered parent plant
  • The genotype of the blue-flowered parent plant
  • The phenotype of the offspring
[3]
b.

State the type of gene interaction shown by the genes D/dD/dD/d and B/bB/bB/b.

[1]
c.

Suggest how the dominant allele DDD inhibits the expression of allele BBB.

[2]
Markscheme

Patterns of inheritance Questions

  1. A Level
  2. /Biology
  3. /Patterns of inheritance

32 exam-style questions on OCR A A Level Biology Patterns of inheritance. Each one has a worked solution and a mark scheme showing where the marks go.

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