Wonder R. J. Palacio

 

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The Punnett Square 
If I have children, there's a one-in-two chance that I will pass on the defective 
gene to them. That doesn't mean they'll look like August, but they'll carry the 
gene that got doubledosed in August and helped make him the way he is. If I
marry someone who has the same defective gene, there's a one-in-two chance 
that our kids will carry the gene and look totally normal, a one-in-four chance 
that our kids will not carry the gene at all, and a one-in-four chance that our kids
will look like August.
If August has children with someone who doesn't have a trace of the gene, 
there's a 100 percent probability that their kids will inherit the gene, but a zero 
percent chance that their kids will have a double dose of it, like August. Which
means they'll carry the gene no matter what, but they could look totally normal. If 
he marries someone who has the gene, their kids will have the same odds as my 
kids.
This only explains the part of August that's explainable. There's that other part of 
his genetic makeup that's not inherited but just incredibly bad luck.
Countless doctors have drawn little tic-tac-toe grids for my parents over the 
years to try to explain the genetic lottery to them. Geneticists use these Punnett 
squares to determine inheritance, recessive and dominant genes, probabilities 
and chance. But for all they know, there's more they don't know. They can try to 
forecast the odds, but they can't guarantee them. They use terms like "germline 
mosaicism," "chromosome rearrangement," or "delayed mutation" to explain 
why their science is not an exact science. I actually like how doctors talk. I like 
the sound of science. I like how words you don't understand explain things you 
can't understand. There are countless people under words like "germline 
mosaicism," "chromosome rearrangement," or "delayed mutation." Countless 
babies who'll never be born, like mine.