• Deyaanjali D.
• Views(1935)

Hi I'm Deya, a second year medical student at Oriel College and I'm going to give you an example of an interview question you can expect as an Oxbridge medical interview.

So here is a pedigree chart of the inheritance of a genetic disease. Explain how this disease is inherited. So my first tip is to think out loud and consider the different modes of inheritance that you know of. For example, you have autosomal or x-linked conditions. And given that there are affected females, it is unlikely to be x-linked recessive. Why? Because females have two copies of the X chromosome and would get one normal copy from the unaffected father. It is unlikely to be x-linked dominant as in the son, having received only a mutated copy of the X chromosome, would not be compatible with life.

If autosomally inherited with recessive conditions, there's a 25% chance of being affected and, with dominant conditions, there is a 50% chance that the children are affected assuming the unaffected father is not a carrier and is homozygous for the normal allele. A helpful way to figure this out would be by drawing out little plots and showing them to the interviewer to explain how you work through the process of working out the probabilities of there being a carrier or an affected person.

So we've already eliminated the possibility of x-linked inheritance. But based on the second generation, it may be autosomal. However, looking at the third generation there seems to be a clear pattern of unaffected and affected clusters of offspring. The affected males have completely unaffected offspring while the affected females have affected offspring. And this is unusual for autosomal inheritance because we've already established the 25% or 50% of probability of being affected. So let's have a closer look at which sex is affected by the condition. In the first generation, it's the mother who passes on the condition to all her offspring. And in the second generation, only the female offspring pass on the condition. And all their children are affected. So the condition seems to be passed on by females only but both sexes can be affected. And it isn't x-linked. It's unlikely to be autosomal. So what other mode of inheritance is there? Now is the time you could potentially get stuck. This question is difficult because it forces you to use your knowledge to work through what you know and apply it into a different and difficult context. However the interviewers are there to help you through and give you support where you get stuck. So another tip here is not to panic and freeze and stop talking. You will inevitably come across hurdles in the interviews because they're meant to stretch you and find the limits of your knowledge and see how you cope with the unknown. So just think of it as a demo tutorial and don't be afraid to ask questions or let these interviewers know when you're unsure.

So at this point you can start thinking out loud about what other type of genetic inheritance you know of. How else are the genes passed on? Autosomal and x-linked inheritance is chromosomal and chromosomal inheritance involves nuclear DNA. But where else in the cell is DNA found? Mitochondria. A mitochondrial DNA is also passed onto the offspring but only via paternal inheritance. And this is because nuclear DNA is passed onto the egg cell from the sperm during fertilization but no mitochondrial DNA. And for this pedigree mitochondrial inheritance seems most likely.

So that's the end of the work through example and I hope you find this video very useful and the tips I've mentioned useful as well. These are the sorts of things that helped me prepare for my interviews and work through each question on the spot. And it's important to remember the interviews are ultimately there to guide you through the whole process so it may seem daunting at first but really make sure to enjoy this opportunity and this experience to have a discussion with experts in your field.

So I hope this was helpful and if you have any more questions, please contact Oxbridge Solutions thank you.