Lesson 3.2.1

3.2.1 Specialised mammalian gametes and fertilisation Quiz: Pearson Edexcel Biology A (Salters-Nuffield), Unit 3

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.2.1, Specialised mammalian gametes and fertilisation: 20 multiple choice questions for the Pearson Edexcel Biology A (Salters-Nuffield) (9BI0), Unit 3: Voice of the Genome, written with Revision Ninja.

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The 20 questions

  1. What is the function of the acrosome in a mammalian sperm?

    • It carries the paternal mitochondria into the egg
    • It propels the sperm through the cervix
    • It contains enzymes that digest the outer layers of the egg so the sperm can penetrate
    • It stores energy as glycogen for the journey

  2. What is the zona pellucida?

    • The plasma membrane of the sperm cell
    • The layer of cells lining the uterus
    • A hormone released by the ovary at ovulation
    • A glycoprotein layer around the egg that sperm must bind to before fertilisation

  3. Which organelle in the sperm midpiece provides the energy for movement?

    • Lysosomes
    • Mitochondria
    • Nucleus
    • Acrosome

  4. What is the cortical reaction in the egg?

    • Release of enzymes that modify the zona pellucida so that other sperm cannot bind
    • Stopping ovulation in the ovary
    • Triggering of meiosis in the sperm nucleus
    • Formation of the acrosome in the egg

  5. Why is the mammalian egg much larger than the sperm?

    • It is produced continuously throughout the female's life
    • It stores nutrients and cytoplasm to support early development
    • It contains no mitochondria of its own
    • It contains more chromosomes than the sperm

  6. Which event occurs first during fertilisation?

    • Fusion of the sperm and egg nuclei
    • The acrosome reaction, releasing enzymes to penetrate the zona pellucida
    • Implantation of the embryo in the uterus
    • The cortical reaction in the egg

  7. What happens after the sperm and egg plasma membranes fuse?

    • The egg loses its nucleus into the uterus
    • The sperm nucleus enters the egg and the two nuclei fuse
    • The sperm sheds its flagellum into the egg
    • The zygote is immediately implanted in the uterine wall

  8. What mechanism prevents polyspermy in mammals?

    • Meiosis in the sperm, which halves the chromosome number
    • The acrosome reaction, which destroys all other sperm
    • The cortical reaction, which hardens the zona pellucida
    • Cell division of the egg, which removes extra sperm

  9. How many chromosomes does a human sperm carry?

    • 22
    • 92
    • 23
    • 46

  10. A somatic cell in a man has 46 chromosomes. How many chromosomes are in one of his sperm?

    • 46
    • 92
    • 12
    • 23

  11. Which feature of the acrosome reaction ensures species specificity of fertilisation?

    • The acrosome prevents the egg from being released
    • The acrosome allows any sperm to fuse with any egg
    • Zona pellucida glycoproteins bind receptors on sperm of the same species, so only compatible sperm usually fertilise the egg
    • The acrosome changes the egg's chromosome number

  12. After the cortical reaction, what happens to the zona pellucida?

    • It becomes thicker and absorbs sperm into its matrix
    • It dissolves completely so that all sperm can enter
    • It hardens and changes so that other sperm can no longer bind
    • It is replaced by a new membrane made of cholesterol

  13. Why are sperm produced in very large numbers?

    • A sperm needs many nuclei to fertilise one egg
    • Large numbers of sperm are needed to build the zona pellucida
    • Most sperm are lost or fail to reach or penetrate the egg
    • Sperm divide by mitosis after release from the testes

  14. A sperm lacks a functional acrosome. Which step of fertilisation is most directly affected?

    • Fusion of the nuclei after the sperm enters the egg
    • Movement of the sperm using its flagellum
    • Penetration of the zona pellucida
    • The cortical reaction in the egg

  15. What is the chromosome number of the zygote formed at fertilisation?

    • The full diploid number for the species
    • Zero, because the nuclei are removed
    • Twice the diploid number, from both gametes
    • Half the diploid number, since it is haploid

  16. Why might a sperm with a defective flagellum fail to fertilise an egg?

    • It cannot undergo meiosis to form haploid cells
    • It cannot synthesise the enzymes in its acrosome
    • It cannot carry any DNA into the egg
    • It cannot reach the egg at the site of fertilisation in the oviduct

  17. What ensures that the sperm's DNA enters the egg?

    • The acrosome itself, which carries the DNA into the egg
    • The cortical granules, which pull the nucleus inside
    • Hardening of the zona pellucida around the sperm head
    • Fusion of the plasma membranes followed by entry of the sperm nucleus

  18. What is the first event after the fusion of the nuclei to form the zygote?

    • Formation of a new acrosome in the zygote
    • Meiosis in the zygote to halve the chromosome number
    • Shedding of the zona pellucida immediately
    • The first mitotic division of the zygote

  19. Which statement is true of both sperm and egg?

    • Both are diploid cells
    • Both are produced continuously throughout adult female life
    • Both have flagella for movement
    • Both are haploid gametes

  20. Why does the sperm midpiece contain many mitochondria?

    • To store the DNA that the zygote will receive
    • To make the enzymes used in the acrosome reaction
    • To produce the zona pellucida around the egg
    • To generate ATP that powers the beating of the flagellum

All Pearson Edexcel Biology A (Salters-Nuffield) quizzes