Free Interview Resources
Free practice questions, preparation advice, and expert insights for Biological Sciences interviews at Imperial College London.
Real Biological Sciences interview questions in the style Imperial College London asks. Try answering each one aloud before you reveal the hint.
A population of 10,000 people is in Hardy-Weinberg equilibrium for a recessive allele. 1 in 100 individuals shows the recessive phenotype. Without a calculator, estimate the frequency of heterozygous carriers.
Problem-Solving
Hint
Set q squared = 0.01 so q = 0.1 and p = 0.9; carrier frequency is 2pq. Show you can move between phenotype frequency and allele frequency cleanly.
An enzyme-catalysed reaction has a Km of 2 mM and Vmax of 100 units. What is the reaction rate at a substrate concentration of 2 mM, and roughly what concentration would you need to reach 90% of Vmax?
Problem-Solving
Hint
At [S] = Km the rate is exactly Vmax/2. Rearrange the Michaelis-Menten equation to see [S] = 9 Km gives 90% of Vmax; reason with the ratio rather than reaching for algebra you cannot check.
A bacterial culture doubles every 20 minutes. Starting from a single cell, roughly how many cells are there after 3 hours, and why does real growth eventually deviate from this?
Problem-Solving
Hint
Nine doublings gives 2 to the ninth, about 500. The interesting part is the follow-up: nutrient limitation, waste accumulation and quorum effects flatten the exponential into a sigmoid.
A gel shows a restriction digest producing fragments of 2, 3 and 5 kb from a 10 kb linear DNA fragment cut by a single enzyme. How many cut sites are there, and where are they? Now suppose the molecule were circular instead — how does your answer change?
Problem-Solving
Hint
Linear: three fragments means two cuts; total must sum to the parent length. Circular: n cuts give n fragments, so three fragments means three cuts. Push the candidate to notice the geometry difference.
Natural selection is often summarised as 'survival of the fittest'. In evolutionary biology, what does 'fitness' actually mean, and why is that phrase misleading?
Conceptual Reasoning
Hint
Steer toward fitness as reproductive success (relative contribution to the next generation's gene pool), not strength or longevity. A sterile 'strong' organism has zero fitness.
Structured interviews that combine technical problem-solving with motivation and personal statement discussion.
Imperial interviews vary by department. Engineering and Computing tend to be technical with problem-solving elements. Medicine uses a Multiple Mini Interview (MMI) format with several short stations. Most interviews last 15-30 minutes and may include a presentation or group exercise.
Interview Invitation
Late Nov
Arrival to Interview
Early Dec
Technical Question
Mid Dec
Decision
Early Jan
Interview Invitation
Late Nov
Arrival to Interview
Early Dec
Technical Question
Mid Dec
Decision
Early Jan
Why is it thermodynamically 'expensive' for a cell to maintain a resting membrane potential, and what would happen to that potential if you poisoned the Na+/K+ ATPase?
midHint
Link ATP hydrolysis to the pump maintaining ion gradients against entropy. Blocking it collapses gradients slowly as passive leak dominates; ask them to reason about timescale, not just direction.
DNA and RNA differ by a single oxygen on the sugar and by uracil versus thymine. Why might evolution have selected DNA as the primary information store and RNA as the working intermediate?
midHint
The 2'-OH makes RNA more reactive and less stable; thymine (methylated uracil) resists a common deamination error. Reward reasoning that connects chemistry to fidelity of long-term storage.
A gene knockout in a mouse produces no visible phenotype. Give three distinct biological explanations for why an essential gene might appear dispensable.
hardHint
Look for genetic redundancy/paralogues, conditional essentiality (phenotype only under stress), and compensatory network rewiring. Strong candidates distinguish 'no phenotype' from 'no measured phenotype'.
Your personal statement mentions wider reading in biology. Take one idea from something you read and explain what you did not understand about it, and how you tried to resolve that.
entryHint
The point is intellectual honesty. Reward a candidate who names a genuine confusion and shows a process of resolving it rather than reciting a summary.
Biological Sciences at Imperial is quantitative and research-led. What draws you to studying biology through data and mathematics rather than as a descriptive science?
midHint
Connect to the course's emphasis on modelling, statistics and molecular mechanism. Look for a concrete example where quantifying a biological system changed the candidate's understanding.
If you had unlimited resources and one year, what biological question would you try to answer, and how would you begin?
midHint
Assess whether they can narrow a grand ambition into a tractable first experiment. A good answer states a hypothesis and a measurable outcome, not just a topic.
Tell me about a time your first interpretation of a result or observation turned out to be wrong. What changed your mind?
hardHint
This probes scientific temperament. Reward evidence-driven revision and the ability to articulate what specific data overturned the prior view.
Roughly how many cells are in your body, and how would you go about estimating that from first principles?
midHint
Look for a Fermi approach: body mass, typical cell mass or volume, and a sanity check against the accepted order of magnitude (around 10 to the thirteenth). The method matters more than the number.
Why are there no wheeled animals in nature, despite the wheel being such an efficient human invention?
midHint
Reward reasoning about the developmental and physiological problem of supplying a freely rotating part with blood and nerves, plus the fitness landscape offering no gradual path. There is no single 'right' answer.
If life were discovered on another planet using a different set of amino acids, what features of our own biochemistry would you still expect it to share, and which are likely accidents of history?
hardHint
Separate physical necessity (a solvent, an energy gradient, information storage) from frozen accidents (the specific genetic code, chirality). Watch how they justify each side of the line.
CRISPR gene editing could remove a heritable disease allele from an embryo. What distinguishes an ethically defensible use of this technology from an indefensible one?
midHint
Draw out the therapy-versus-enhancement line, consent of future generations, and germline versus somatic editing. Reward a candidate who can argue the hard cases, not just assert a position.
A new gene-drive could eradicate the mosquito species that transmits malaria. Should we deploy it? Walk me through the biological risks as well as the ethics.
hardHint
Look for ecological reasoning about food webs and niche vacancy alongside the humanitarian case, plus irreversibility and cross-border governance. Strong answers weigh uncertainty explicitly.
Should scientists publish research that identifies how to make a pathogen more transmissible? Argue both sides.
hardHint
This is the dual-use dilemma. Reward balancing open science and pandemic preparedness against bioterrorism and accidental release, and a candidate who can commit to a defensible middle position.
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