Lesson 3.5.1

3.5.1 Genotype, environment, epigenetics and polygenic variation 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 3.5.1, Genotype, environment, epigenetics and polygenic variation: 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 a phenotype?

    • The alleles an organism carries at a particular locus
    • The number of chromosomes in a cell
    • The sequence of nucleotides in a gene
    • The observable characteristics of an organism that result from its genotype and environment

  2. Which term describes a trait controlled by multiple genes with a continuous distribution?

    • Sex linkage
    • Codominance
    • Polygenic inheritance
    • Monohybrid inheritance

  3. What does an epigenetic change involve?

    • A change in the sequence of bases in the DNA
    • Changes in gene expression, such as DNA methylation, without a change in the DNA sequence
    • The fusion of two gametes to form a zygote
    • The loss of a whole chromosome from the cell

  4. What effect does DNA methylation usually have on gene expression?

    • It always increases the expression of every gene it touches
    • It usually reduces or silences expression of the methylated gene
    • It converts DNA into RNA
    • It changes the sequence of the codons in the gene

  5. How do histone modifications such as acetylation affect gene expression?

    • Acetylation prevents any RNA from being made
    • Acetylation changes the DNA sequence in the coding region
    • Acetylation tightly packs DNA and permanently deletes the gene
    • Acetylation loosens chromatin, usually making genes more accessible for transcription

  6. Identical twins raised in different environments may show different phenotypes. What explains this?

    • Their mitochondria have different genotypes
    • Their DNA sequences differ after birth
    • Their ribosomes have different alleles
    • Their environments and epigenetic differences can alter gene expression, despite identical DNA

  7. Why is continuous variation typical of polygenic traits?

    • Each gene produces exactly one phenotype with no overlap
    • Many genes each add a small effect
    • Environmental factors have no effect on polygenic traits
    • Continuous variation only occurs in asexual organisms

  8. Which pattern would you expect for a polygenic trait such as human height in a large population?

    • A bell-shaped, roughly normal distribution of values
    • A single value shared by every individual
    • Two distinct groups with no individuals in between
    • A sharp spike at one extreme of the range

  9. Which factor can affect the phenotype of an organism without changing its genotype?

    • A mutation in the coding region of a gene
    • Crossing over during meiosis
    • Diet and exposure to sunlight
    • Replacement of a chromosome during fertilisation

  10. What is the role of epigenetic changes that are passed on after cell division?

    • They allow a daughter cell to inherit the same pattern of gene activity as its parent
    • They remove all gene expression from the daughter cells
    • They ensure that daughter cells have different chromosome numbers
    • They change the DNA sequence in every daughter cell

  11. A trait is influenced by alleles at 10 loci, each with a small additive effect. What is the expected outcome?

    • A phenotype determined only by the environment
    • A wide range of phenotypes with many intermediate values
    • Only two phenotypes, one for each allele at the locus
    • A single phenotype identical for all individuals

  12. Which statement describes genotype correctly?

    • The observable appearance of an organism, unaffected by its genes
    • The proportion of heterozygotes in a population
    • The number of individuals in a habitat
    • The genetic make-up of an organism

  13. Which of these is a documented example of an environmental effect on phenotype?

    • Blood group determined by a single locus with three alleles
    • Hydrangea flower colour depending on soil pH
    • Fruit fly eye colour determined by mitochondrial DNA
    • Eye colour determined only by the Y chromosome

  14. Which statement about DNA methylation and cell division is correct?

    • Methylation patterns can be maintained through cell divisions
    • Methylation only occurs in cells that have stopped dividing
    • Methylation changes the number of chromosomes in each daughter cell
    • Methylation is lost completely with every cell division

  15. Why does the same genotype produce different phenotypes in different environments?

    • The environment replaces alleles in the DNA
    • The genotype changes as soon as the environment changes
    • The phenotype is fixed at fertilisation and never changes
    • Environmental factors can change the activation of genes

  16. Which of these is most likely to be a polygenic trait?

    • The ABO blood group
    • Sex determination in humans
    • Presence or absence of a single recessive disease
    • Human skin colour

  17. Which of these is best described as an environmental influence on phenotype?

    • Scarring of the skin following a burn injury
    • Red-green colour blindness carried on the X chromosome
    • Eye colour set by melanin genes
    • The ABO blood group produced by the I gene

  18. What does the term 'epigenome' refer to?

    • The set of chemical marks on DNA and histones that regulate gene activity
    • The population of organisms living in an ecosystem
    • The set of proteins that build cell membranes
    • The complete set of DNA sequences in an organism

  19. Which type of variation is produced by a single gene with two alleles, with no environmental effect?

    • Discontinuous variation, with distinct discrete classes
    • Variation caused only by epigenetic marks
    • Variation caused by the environment alone
    • Continuous variation in a bell-shaped curve

  20. Why might a polygenic trait be affected by both genotype and environment?

    • Environmental factors affect only single-gene traits
    • Polygenic traits are determined completely by the environment
    • Environmental factors can alter how genes are expressed
    • Polygenic traits cannot be influenced by anything other than genes

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