Day 30 marks the beginning of Chromosome 2. This is a fascinating chromosome because it is the only one found in humans but not our primate relatives: it resulted from the fusion of two ancestral chromosome.
Today has 23 protein-coding genes including ALLN, encoding the enzyme allantoicase. In fish and amphibians, allantoicase breaks down uric acid. In land vertebrates, this function has been taken over by other enzymes; in humans, it is lost (we excrete uric acid in our urine.)
Usually when a gene loses its necessity during evolution, it becomes a pseudogene, inactivated by random mutations, living on only as a genetic fossil. (The GULO pseudogene is an example – it gave our ancestors the ability to synthesize vitamin C.) ALLN is not a pseudogene because it actually makes a protein product still, and for some reason it has not accumulated the early stop codons that would ordinarily doom a pseudogene to nonsense-mediated decay. It may have gained a secondary function unrelated to uric acid metabolism, or a quirk of being near especially important genes may have kept it relatively mutation-free through a process called background selection.
Click here to see your ALLN gene at the start of Chromosome 2.