Oxford Biochemistry Interview Questions

Getting ready for your Oxford interview? Our list of Oxford Biochemistry interview questions contains real questions from past interviews as well as an example question with a detailed worked solution from an Oxbridge interview tutor.

We recommend that you review the worked solution first to see the type of thinking admissions tutors are looking for at interview. Then have a go at some of the questions listed below. However, our advice is to use these to practise ways of approaching questions rather than trying to rehearse and memorise answers. The chances of one of these exact questions occurring in your Oxford Biochemistry interview is very low, and even if it were to come up, then Oxford tutors can spot prepared answers and look unfavourably upon them.

Example Interview Question with Worked Solution

Is this disease dominant or recessive?

This Oxford Biochemistry interview question is really testing your abilities to think logically, since it doesn’t actually require any scientific knowledge, other than an understanding of basic Mendelian genetics (covered on most GCSE courses). Being able to think logically is a prerequisite of studying science and is therefore often tested at interview. Working through this question helps to illustrate how to structure questions that are not based on pre-existing knowledge, but are instead designed to see how you think.

The key to answering such a question is not to jump in with an answer – it is highly unlikely that you will be given a question like this in an Oxbridge interview if a definitive answer can be reached very quickly. It is also very important to show your interviewer your thought process – including ‘exploratory thoughts’ which may, or may not, prove fruitful. There is no discredit in abandoning an unproductive line of thought; indeed, showing that you have a sense of when it becomes clear that it IS unproductive is just as important as alighting on a productive line of thought straight away.

So where should you begin with a question like this? There are of course a number of different ways of tackling the question. The question is asking whether the disease is dominant or recessive. So an appropriate first stage would be to consider whether the genetic tree diagram makes sense if the disease is dominant; and to do this using a structured method.

The first question you would be asking is: does the genetic tree diagram make sense if the disease is dominant? In order to work this out, we must begin by establishing what the different genotypes in the tree will be. Let’s label the dominant allele A and the recessive allele a. If the disease is dominant, normal individuals will therefore have genotype aa. Sufferers, on the other hand, could have genotype AA or could have genotype Aa. We then begin working through the tree. Again, try pausing here and working from Generation 1 down the tree to see whether it makes sense for the disease to be dominant.

Working through the tree should yield the following conclusions:

• In generation 1 the man is AA/Aa and the woman is aa.
• The offspring in generation 2 are both sufferers. Since they must have received a recessive (a) allele from their mother, and they are sufferers, we know that their exact genotype must be Aa. (At an additional level of analysis we could note that if the man in generation 1 was AA we would have expected 100% Aa in the offspring. If on the other hand the man in generation 1 was Aa we would expect only 50% in the offspring. It is therefore more likely that the first man’s genotype was AA.
• All of the offspring in generation 3 are therefore born from a cross between Aa and aa. We would therefore expect 50% of them to be sufferers. In fact, 100% are sufferers. This is not the most likely outcome from such a cross; but it is still possible that the disease could be dominant.
• The offspring in generation 4 have also all been born from a cross between Aa and aa, which would be expected to give 50% of sufferers. Here, 6 out of 8 of the children are sufferers. This is consistent with the disease being dominant.
• The same again applies to the offspring in generation 5 as to the offspring in generation 4.

Conclusion: It is possible that the disease is dominant.

Does the genetic tree diagram make sense if the gene is recessive? Again, it is important to begin by considering what the genotypes would be if the disease were recessive. Sufferers would have genotype aa, whilst non-sufferers could be AA or Aa (carriers).

• In generation 1 the man is aa and the woman is Aa/AA.
• The offspring in generation 2 are both sufferers. The woman in generation 1 therefore MUST have had phenotype Aa in order for the offspring to receive two recessive alleles, and all the offspring in generation 2 have genotype aa.
• The offspring in generation 3 are also all sufferers. The two individuals who marry into the family therefore MUST have had phenotype Aa. (Note that again we would have expected 50% to be sufferers instead of 100%. Therefore, the ratios observed are of the same likelihood whether the disease is dominant or recessive and do not help to choose between them.)
• There are sufferers in generation 4. Therefore, again the individuals that marry into the family MUST have had phenotype Aa.
• There are sufferers in generation 5. Therefore, the individuals that marry into the family MUST have had phenotype Aa.

Conclusion: It is possible that the disease is recessive: however, this requires making the assumption that every individual marrying into the family is a carrier of the disease. The above would therefore form a well-structured answer to the question posed; though such an answer would often be reached with guidance from the interviewer.

This answer raises the question of how much of an assumption it is to assume that the individuals marrying into the family are carriers of the disease; which creates a more biological aspect to this question. Try and think about whether this is a big assumption to make (and therefore highly unlikely to be valid) before reading the following.

This question requires you to think about why there are carriers present in the population. To decide whether it is a big assumption to make would require some knowledge of the disease. If the disease is very rare and having the gene for the disease is in no way beneficial from an evolutionary perspective then assuming such a prevalence of carriers would be a big assumption to make.

However, there are diseases where being a carrier is very beneficial from an evolutionary perspective. The most common example of this is sickle cell anaemia. In sickle cell anaemia, changes in the carriers’ red blood cells mean that the malarial parasite cannot complete part of its life cycle. Therefore, if someone in a malaria-endemic population is reproducing, it could in fact be argued that it is more likely that they are a carrier, since if they weren’t a carrier they would have had an increased risk of malaria and an increased risk of not reaching child-bearing age.

This illustrates how pre-existing knowledge can be applied to new situations in the science interview questions faced at Oxbridge.

Past Oxford Biochemistry Interview Questions

The following Oxford Biochemistry interview questions have come up in Oxbridge interviews in recent years. We strongly recommend, however, that you use these to help you to think laterally about your chosen subject rather than learn and rehearse answers to them.

• Why should you have a place rather than everyone else?
• What do you like and dislike about biochemistry?
• Why did you choose Biochemistry and not Medicine?
• Questions on virus structure and function.
• Questions on DNA replication and protein synthesis – structure of proteins.
• Questions on respiration – processes in cells e.g. glycolysis.
• Questions on bonding in molecules.
• How did the first protocells divide and replicate?
• How does a virus make its cell wall?
• How could synthetic nucleotides be incorporated in protein synthesis?
• Describe a biochemical pathway.
• Draw a peptide bond – is there any rotation around the C-N? Why?
• There are two possible arrangements in one unit of a polypeptide – if there are 100 units, how many possible arrangements are there?
• How/why do proteins fold?
• How would I amplify DNA?
• Questions on equilibrium and factors affecting its position.
• How do amino acids behave in both acidic and basic conditions?
• What is the significance of the human genome project?
• How does DNA fingerprinting work? What is its use?
• How do you tell if a protein codes for a transmembrane protein?
• Why are there so many steps in the cascade of reactions?
• How are proteins altered after synthesis?
• Questions on amino acid structure and function.
• Questions on the mechanism of electrophilic addition.
• Identify and describe the reactions of an aldehyde.
• What are the differences between a human enzyme and the enzymes of bacteria that live in a hot spring?
• Questions on the types of chemical bonds and where they are found (e.g. ionic; covalent; intermolecular forces in proteins).
• Why are there only twenty amino acids?
• There are 10,000 genes but 30,000 proteins in our body. How is this possible?
• Draw and describe the reactions of an amino acid (glycine?) in pH 1, pH 7, and pH 14 conditions. Tell me about any isomerism or rotational symmetry of this compound.
• Discussion about disulphide bridges – which amino acids are required? Name the type of reaction which forms these bonds? Could this occur in cells and which types of proteins have these bonds?
• Here is the skeletal formula of penicillin. Name the functional groups and talk about its behaviour in water.
• How does a penicillin molecule interact with a site on a protein molecule?

How Dukes Plus Can Help

We hope you found practising with these Oxford Biochemistry interview questions useful.

If you’d like specialist coaching for your Oxford interview, our Oxford interview tutoring includes highly realistic full mock interviews plus feedback from our expert team of Oxford-graduate tutors. Some of our packages also include a session with a former admissions tutor at Oxford – someone with direct experience of interviewing candidates for an Oxford college.