Lesson 3.7.1.2

3.7.1.2 Genetic crosses and inheritance patterns Quiz: AQA Biology, Unit 7

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.7.1.2, Genetic crosses and inheritance patterns: 20 multiple choice questions for the AQA Biology (7402), Unit 7: Genetics, populations, evolution and ecosystems, written with Revision Ninja.

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The 20 questions

  1. What is the expected phenotypic ratio in the F2 generation of a monohybrid cross with complete dominance?

    • 9:3:3:1
    • 1:1
    • 1:2:1
    • 3:1

  2. What is the expected phenotypic ratio of a dihybrid cross between two heterozygotes with independent assortment and complete dominance?

    • 1:2:1
    • 3:1
    • 9:7
    • 9:3:3:1

  3. What is crossed with an individual of unknown genotype in a test cross?

    • Homozygous recessive
    • Heterozygote
    • Homozygous dominant
    • Pure breeding dominant

  4. On which chromosome are human sex-linked genes predominantly carried?

    • Mitochondrial DNA
    • X chromosome
    • Autosome
    • Y chromosome

  5. What is the numerator in each term of the chi-squared formula?

    • Observed minus expected
    • Observed squared minus expected
    • Expected minus observed squared
    • Observed minus expected squared

  6. A chi-squared test compares four phenotypic classes. How many degrees of freedom are used?

    • 4
    • 2
    • 3
    • 5

  7. What occurs during genetic epistasis?

    • Crossing over occurs
    • One gene masks another
    • Chromosomes fail to separate
    • One gene duplicates another

  8. What is the probability that a child of two heterozygous parents (Aa x Aa) will be aa?

    • 1/2
    • 1/4
    • 3/4
    • 1/16

  9. What is the expected genotypic ratio from a Bb x bb genetic cross?

    • 3:1
    • 1:2:1
    • 9:3:3:1
    • 1:1

  10. In a dihybrid cross AaBb x AaBb, what is the probability of an aabb offspring?

    • 1/4
    • 1/8
    • 1/16
    • 9/16

  11. In a cross, 70 round and 30 wrinkled seeds are observed from 100 seeds. The expected ratio is 3:1. What is the chi-squared value?

    • 1.33
    • 0.25
    • 5.00
    • 2.67

  12. What conclusion is drawn when chi-squared is less than the critical value?

    • Reject null hypothesis
    • Accept null hypothesis
    • Result is significant
    • Mutation has occurred

  13. A woman who is a carrier of colour blindness (X^c X) has children with a normal man (X Y). What is the probability that a son is colour blind?

    • 0
    • 1/2
    • 1
    • 1/4

  14. Why do linked genes produce fewer recombinant offspring than independent assortment?

    • Inherited together
    • Replication fails
    • Mutate more frequently
    • Located on autosomes

  15. What genetic interaction produces a 9:7 phenotypic ratio in a dihybrid cross?

    • Codominance
    • Complementary gene action
    • Epistasis
    • Sex linkage

  16. A dihybrid cross of 160 offspring is expected to show the double dominant phenotype with 9:3:3:1 ratio. How many offspring should show this phenotype?

    • 40
    • 10
    • 90
    • 60

  17. What is the correct conclusion when a calculated chi-squared value exceeds the critical value?

    • Accept expected ratio
    • Accept null hypothesis
    • Accept alternative hypothesis
    • Reject null hypothesis

  18. A daughter has an X-linked recessive condition. What must be true about her father?

    • Must be a carrier
    • Must be unaffected
    • Must be homozygous
    • Must be affected

  19. What phenotypic ratio is expected from a cross of two heterozygotes for a codominant gene?

    • 1:1
    • 3:1
    • 9:3:3:1
    • 1:2:1

  20. What causes recombinant offspring to appear less frequently than 50 per cent in a test cross?

    • Gene linkage
    • Codominance
    • Polygenic inheritance
    • Independent assortment

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