# The second leading genetic cause of mental retardation is Fragile X The second-leading genetic cause

The second leading genetic cause of mental retardation is Fragile X

The second-leading genetic cause of mental retardation is Fragile X Syndrome, named for the fragile appearance of the tip of the X chromosome in affected individuals. One in 1500 males is affected world-wide, with no ethnic bias.

a. In a sample of 10,000 males, how many would you expect to have Fragile X Syndrome?

b. For a sample of 10,000 males, use the normal approximation to the binomial distribution to determine the probability that more than 7 of the males have Fragile X Syndrome; that at most 10 of the males have Fragile X Syndrome.

c. The probabilities in part (b) were obtained in Exercise 5.109 on page 258 by using the Poisson approximation to the binomial distribution. Which estimates of the true binomial probabilities would you expect to be better, the ones using the normal approximation or those using the Poisson approximation? Explain your answer.

The second leading genetic cause of mental retardation is Fragile X