Video: Example Oxford Biochemistry interview question

https://www.youtube.com/watch?v=18QTPCAiZ0Y

Why does DNA have 4 bases? This is a classic example Oxford biochemistry interview question.

However, this question requires first to consider the 'question before the question', which is what is the structure of DNA? Useful content to mention here is the complementary strands and the codon to anti-codon to amino acid translation process. From this point, it becomes obvious that you can't have a complementary system with an odd number of bases. 2 bases don't allow for enough genetic diversity in a triplet codon system and more than 4 could be argued to be redundant.