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CAIE IGCSE Biology 17.4.12 Punnett Squares

Practise constructing Punnett squares to show all possible genotypes when a cross can produce more than one outcome.

Syllabus
2026–2028
Course
Biology 0610

Exam points

  • place each parental gamete once along the top or side of the Punnett square
  • combine one allele from each parent in every offspring box
  • list each distinct possible genotype without treating repeated boxes as new genotype types

17.4.12—Punnett squares in crosses which question 1

[Maximum number: 3]

The four o'clock plant, Mirabilis jalapa, can have flowers of three different colours as shown in Fig. 4.1.

Fig. 4.1

Fig. 4.1

The student then carried out three further crosses as shown in Table 4.1.

Table 4.1

Table 4.1

Complete the table by writing in the genotypes of the offspring of crosses 2, 3 and 4, using the same symbols as in the genetic diagram in (a).

You may use the space below for any working.

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