Remember gcau, G pairs with C and A pairs with u G-C A-U
C because oxygen was a byproduct of photosynthesis and proved to be EXTREMELY important in the atmosphere.
There is 50% probability that their daughter's son will have the disease, because daughter chromosomes are XX , and the X from father will have x- linked disease, now in next generation the son will have XY chromosomes, Y is from father and X will from mother, now mother have two "XX", out of these two one carry x- linked disease, that means 50 percent chances of having disease in son.
increase because of carbon