Lesson 3.7.1.1

3.7.1.1 Alleles, genotypes and phenotypes Quiz: AQA Biology, Unit 7

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

In partnership with Revision Ninja

Lesson 3.7.1.1, Alleles, genotypes and phenotypes: 20 multiple choice questions for the AQA Biology (7402), Unit 7: Genetics, populations, evolution and ecosystems, written with Revision Ninja.

Host it live on the board and students join with a game code on their own devices, or revise alone with Free Play. The answers are revealed in the game.

Host this setFree Play

The 20 questions

  1. What term describes the genetic constitution of an organism?

    • Phenotype
    • Genotype
    • Genome
    • Karyotype

  2. What term describes the observable characteristics of an organism resulting from its genes and environment?

    • Proteome
    • Genotype
    • Genome
    • Phenotype

  3. What term describes the fixed position of a gene on a chromosome?

    • Centromere
    • Allele
    • Locus
    • Telomere

  4. How are codominant alleles expressed in a heterozygote?

    • Both fully expressed
    • Blending together
    • Neither is expressed
    • One is dominant

  5. What term describes an organism with two identical alleles at a gene locus?

    • Heterozygous
    • Homozygous
    • Polygenic
    • Hemizygous

  6. How many alleles for each gene does a normal diploid somatic cell contain?

    • Two
    • One
    • Three
    • Four

  7. What term describes when more than two alternative forms of a gene exist in a population?

    • Multiple alleles
    • Polygeny
    • Codominance
    • Epistasis

  8. The ABO blood group phenotype AB has which genotype?

    • I^O I^O
    • I^A I^B
    • I^A I^A
    • I^A I^O

  9. A recessive allele for white flowers is r and red is R, with R dominant. Which genotype gives white flowers?

    • Rr and RR together
    • Homozygous dominant RR
    • rr
    • Heterozygous Rr

  10. Humans have how many copies of an autosomal gene in each body cell?

    • 23
    • 4
    • 1
    • 2

  11. Pea seed shape is controlled by R for round and r for wrinkled, with R dominant. Which genotype is a round heterozygote?

    • Homozygous dominant RR
    • Rr
    • rR and rr together
    • Recessive rr

  12. Why does a heterozygote usually show the dominant phenotype?

    • Two active alleles
    • No recessive alleles
    • Sufficient functional enzyme
    • Equal gene expression

  13. What term describes an individual carrying two different alleles at a gene locus?

    • Heterozygote
    • Polygenic
    • Homozygote
    • Hemizygote

  14. An organism with genotype AaBbCc is assumed to show independent assortment. How many different gamete types can it produce?

    • 6
    • 12
    • 3
    • 8

  15. What causes continuous variation in human height across a population?

    • Polygenic and environmental
    • Purely environmental
    • Single gene mutation
    • Strict codominance

  16. Which two genotypes cannot be distinguished by looking at the phenotype alone?

    • Homozygous dominant and heterozygous
    • Codominant and heterozygous
    • Homozygous dominant and recessive
    • Heterozygous and homozygous recessive

  17. Which allele is expressed in the phenotype of a heterozygote?

    • Recessive allele
    • Dominant allele
    • Mutated allele
    • Neither allele

  18. What phenotype is produced by the homozygous recessive genotype aa?

    • Intermediate phenotype
    • Codominant phenotype
    • Recessive phenotype
    • Dominant phenotype

  19. Which factor alters phenotype without changing the underlying genotype?

    • Environmental factors
    • DNA replication
    • Gene mutation
    • Chromosome deletion

  20. Why might identical twins with the same genotype show different phenotypes?

    • Environmental influence
    • Altered alleles
    • Different DNA
    • Mutated chromosomes

All AQA Biology quizzes