Lesson 3.8.4.3.1

3.8.4.3.1 Genetic fingerprinting and its uses Quiz: AQA Biology, Unit 8

20 questions

Written by Revision Ninja · Last reviewed 11 October 2026

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Lesson 3.8.4.3.1, Genetic fingerprinting and its uses: 20 multiple choice questions for the AQA Biology (7402), Unit 8: The control of gene expression, written with Revision Ninja.

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The 20 questions

  1. What are variable number tandem repeats (VNTRs) in the genome?

    • Proteins that are repeated in each cell of the body, forming a large structural complex that is identical in every individual of a species
    • Genes that are repeated in exactly the same number in everyone, so that the copy number is constant between individuals of the same species
    • Single bases that are substituted in every individual at the same site
    • Short sequences repeated a variable number of times at specific sites in the genome

  2. What is the probability of two unrelated individuals having the same VNTR pattern?

    • Equal to the probability of having the same blood group
    • Very low
    • Exactly one half
    • Certain for all individuals

  3. What does gel electrophoresis separate DNA fragments by?

    • Temperature, so cold fragments move furthest
    • Colour, with red fragments moving further
    • Protein content, so proteins move towards the positive electrode
    • Size, with smaller fragments moving further through the gel

  4. What is the usual first step before analysing a small sample in genetic fingerprinting?

    • Remove all the introns from the DNA
    • Amplify the DNA fragments by PCR
    • Convert the DNA into protein
    • Label the DNA with a restriction enzyme

  5. Genetic fingerprinting can be used to determine:

    • Genetic relationships and the genetic variability within a population
    • The colour of the organism's skin and coat, because repeat patterns in the DNA encode pigment that can be read from the bands
    • The number of ribosomes in a cell, which can be counted directly from the banding pattern of the DNA in each sample
    • The exact age of an organism in years, since the number of repeats in its DNA increases steadily with each year of life

  6. Why does DNA move towards the positive electrode during gel electrophoresis?

    • DNA is made of sugar, which is always positive
    • DNA is negatively charged because of its phosphate groups
    • DNA is positively charged because of its bases
    • DNA is attracted to the wells of the gel

  7. Genetic relationships between individuals are shown by:

    • Measuring the length of their limbs
    • Counting the number of cells in each individual
    • Comparing the band patterns produced by their DNA
    • Testing the colour of their blood

  8. A suspect's band pattern matches the crime-scene sample at every band. What is the most reasonable conclusion?

    • The suspect is certainly the source, since a full match at every band means that no further analysis or statistics are needed at all
    • The crime-scene sample must have been contaminated by the suspect's DNA in the laboratory, so the match is worthless as evidence
    • The suspect is likely to be the source, though the probability of a chance match must be assessed statistically
    • The suspect cannot have been at the scene, because a match of bands proves that the sample came from a different individual

  9. In a gel, which fragments travel furthest from the wells?

    • All fragments travel the same distance
    • Only fragments containing introns
    • The smallest fragments
    • The largest fragments

  10. Two individuals share 8 of 10 bands in a fingerprint. What percentage of bands is shared?

    • 8 per cent
    • 80 per cent
    • 10 per cent
    • 20 per cent

  11. Why are VNTRs useful for genetic fingerprinting?

    • They are only found in the mitochondrial genome, so they can be inherited only from the mother and never from the father
    • They vary in repeat number between individuals, so they produce distinctive banding patterns
    • They are identical in all individuals of a species, so they give the same banding pattern for every person who is tested
    • They code for the same protein in every individual, so the protein's amino acid sequence reveals who the sample came from

  12. Why might genetic fingerprinting be used in animal breeding?

    • To change the colour of the animal's coat directly, by using the fingerprint bands to select the pigment genes for a new coat colour
    • To produce animals without any parents, because the fingerprint allows a breeder to grow offspring from a single cell in the laboratory
    • To remove all disease from the herd in one generation, since the fingerprint can detect every infection that the animals carry
    • To confirm parentage and to measure genetic diversity within a breeding population

  13. Two DNA samples have identical bands, except that one has an extra band. What is the most reasonable conclusion?

    • The samples must come from identical twins, because identical twins share every band and so the extra band must be a rare mutation
    • The samples are unlikely to come from the same individual, unless contamination or error is responsible
    • The extra band means that gel electrophoresis has failed completely, so the results from this run cannot be used for any comparison
    • The extra band shows that both samples are from a single individual, since one person can produce two different banding patterns

  14. Why is PCR used on a very small sample before fingerprinting?

    • It removes all DNA from the sample
    • It converts the DNA into protein for analysis
    • It amplifies the DNA so that there is enough material to analyse
    • It labels the DNA with a radioactive tag only

  15. Which principle underpins genetic fingerprinting?

    • All individuals have identical DNA at every locus, so the banding patterns of different people are expected to be the same
    • Individuals have different numbers of repeats at the same locus, so their banding patterns differ
    • Banding patterns depend only on the age of the individual, so people of the same age produce matching fingerprints in the gel
    • Banding patterns are produced only by the mitochondrial DNA, which is identical in every person and so gives the same bands always

  16. Why is a genetic fingerprint match described as probabilistic rather than certain?

    • A match depends on the probability that unrelated people share the same bands in a population
    • A match is only possible for identical twins, since they alone share the repeats that are needed to produce the same banding pattern
    • A match is always certain because DNA is identical in everyone, so any two samples that are compared must always give the same bands
    • A match is never possible between two individuals, because every banding pattern is unique

  17. Three independent loci each have a 0.1 probability of matching by chance between two unrelated people. What is the probability that all three match?

    • 0.01
    • 0.0001
    • 0.3
    • 0.001

  18. Put these steps in the most likely order: 1 extract DNA, 2 amplify VNTR regions by PCR, 3 separate fragments by gel electrophoresis, 4 compare band patterns. Which sequence is correct?

    • 4, 3, 2, 1
    • 2, 1, 3, 4
    • 1, 2, 3, 4
    • 1, 3, 2, 4

  19. Why must control samples be run alongside test samples in gel electrophoresis?

    • To make the samples move faster through the gel, so that the whole run takes less time and the bands are sharper
    • To ensure that all samples have identical DNA, so that every sample must produce exactly the same banding pattern
    • To check that the banding is due to the samples themselves and not to contamination or error
    • To remove the VNTRs from the samples before they are loaded, so that only the non-repetitive DNA is analysed

  20. How can genetic fingerprinting show genetic variability within a population?

    • Comparing band patterns across individuals shows how many different repeat numbers and alleles are present
    • Genetic fingerprinting shows only the age of individuals in the population
    • Each individual in a population has exactly the same banding pattern, so the fingerprint cannot distinguish any member from any other
    • Genetic fingerprinting only shows the sex of individuals in the population, since the bands reveal only which chromosomes are present

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