how many copies of tp53 (p53) gene do we have?

Question

I just started studying biology so I almost have no knowledge.

I learned about the tp53 gene and I just wanted to know how many copies of tp53 gene we have?

Answer 1

Humans have one copy of the p53 gene per set of chromosomes along with most other mammals (a notable exception being elephants with 20)^[1]. Since it is located on an autosome (chromosome 17), each parent gives one copy of the gene^[2]. Meaning two copies per human cell (and 40 per elephant cell).

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A little extra information on p53 and the effects of only having 2 copies:

Since humans only have two copies per cell and p53 forms a homo-tetramer, it only takes one mutated copy to lose functionality.^[3] This is because p53 needs to tetramerize to function, meaning only 1 out of 16 p53 proteins are effective if one copy is mutated (2⁴ possibilities and only 1 combination has 0 mutated copies, ~6% are functional). This makes p53 a rare human tumor-suppressor gene with dominant negative mutations.

But with elephants, the more copies they have, the less and less one mutation affects the amount of functional p53. ($\bigl( \frac {39}{40}\bigr)$⁴ probability of having a functional tetramer = 90% functional, which is very high)