2.5.1 Monohybrid inheritance and pedigree diagrams Quiz: Pearson Edexcel Biology, Unit 2

The 20 questions

1. What term describes an allele that is expressed in a heterozygous individual?

   • Dominant
   • Epistatic
   • Co-dominant
   • Recessive

2. What is the expected phenotypic ratio in the offspring of two heterozygous parents for a single gene with complete dominance?

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

3. What genotype is crossed with an organism in a test cross?

   • Homozygous dominant
   • Homozygous recessive
   • Heterozygous recessive
   • Heterozygous dominant

4. What phenotype ratio comes from crossing two pink-flowered plants showing incomplete dominance?

   • 1 red:1 white
   • 1 red:2 pink:1 white
   • 3 pink:1 white
   • 3 red:1 white

5. In a pedigree diagram, how is a female individual usually represented?

   • A triangle
   • A circle
   • A square
   • A diamond

6. Two unaffected parents have an affected child. What genotype must both parents have?

   • Homozygous dominant
   • Hemizygous carriers
   • Homozygous recessive
   • Heterozygous carriers

7. Which term describes the allele combination present in an organism for a gene?

   • Genotype
   • Phenotype
   • Karyotype
   • Genome

8. Which parental genotype combination can produce a child with an autosomal recessive condition?

   • Homozygous dominant
   • Unaffected father
   • Two carriers
   • Homozygous recessive

9. Two heterozygous parents for a recessive condition have a child. What is the probability that the child is a carrier but not affected?

   • 1/8
   • 1/2
   • 1/4
   • 3/4

10. A pedigree shows an autosomal dominant trait that appears in every generation. What is the chance that an affected parent who is heterozygous has an affected child?

    • 75%
    • 50%
    • 25%
    • 100%

11. In a monohybrid cross between two heterozygotes, what proportion of offspring are homozygous recessive?

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

12. A dominant allele A and recessive allele a control a plant trait. A heterozygote is crossed with a homozygous recessive plant. What is the phenotypic ratio of the offspring?

    • 1 dominant : 1 recessive
    • All dominant
    • 3 dominant : 1 recessive
    • All recessive

13. A geneticist finds that 25% of offspring from a cross between two carriers show a recessive phenotype. Which ratio does this match?

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

14. What is the genotype of all F1 offspring from an AA and aa cross?

    • Homozygous dominant
    • Homozygous recessive
    • Hemizygous
    • Heterozygous

15. Unaffected parents have two affected daughters. Which pattern of inheritance is shown?

    • Autosomal recessive
    • Sex-linked dominant
    • Y-linked
    • Autosomal dominant

16. In a standard pedigree diagram, what does a shaded symbol represent?

    • An affected individual
    • A carrier individual
    • An unaffected individual
    • A deceased individual

17. In a monohybrid cross with incomplete dominance, what phenotypic ratio results from the F2 generation of pink x pink?

    • 3 red : 1 white
    • 1 red : 2 pink : 1 white
    • 2 red : 2 white
    • 1 red : 1 white

18. Which of these terms refers to a pair of alleles that are the same at a locus?

    • Homozygous
    • Mutant
    • Dominant
    • Heterozygous

19. Which inheritance pattern typically allows a genetic condition to skip generations?

    • Codominant
    • Autosomal dominant
    • Incomplete dominance
    • Autosomal recessive

20. Two heterozygous parents have three children. What is the probability that all three children are affected by a recessive condition?

    • 1/16
    • 1/4
    • 1/64
    • 3/64

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