Question

Scientists recently discovered that elephants have 40 copies of the p53 gene, while humans have two copies (one from our biological mother and one from our biological father).

Use the language of biology to explain how this discovery could explain why so few elephants die from cancer.

Answer 1

P 53 is a tumour suppressor gene. The function of P53 in a cell is to Regulate cell cycle. Regulation of cell cycle prevents neoplastic transformation. Any damage to the DNA triggers the expression of P53 gene. This increases P53 levels in the cell.This prevents cell from entering 'S' phae of the cell cycle which gives time for the cell to repair the DNA damage. Once the DNA is repaired, P53 is degraded and the cell cycle continues. If the damage to DNA is not repaired, it leads to apoptosis of the cell. This is how it maintains a stable genome and for this reason P53 gene is called as the guardian of the genome.

Mutations in P53 are related to number of human cancers such as breast cancer, colorectal cancer, lung and liver cancers etc.

Humans have only two alleles of P53 in each cell. If these alleles mutate, there is no cell cycle regulation. Which means the cell cycle will progress with damaged DNA leading to neoplastic transformation of the cell. While elephants have 40 copies of P53 genes in a cell. So, any mutation in one of these alleles can only be expressed very rarely because all other alleles are normal and not mutated. In most of the cases even if mutations do occur, P53 gene will be working normally. That is why cancers are rare in elephants. Less mutations affecting the P53 gene expression, there is less likely that the organism suffers from cancer. That is why elephants do not suffer from cancer.