While Sid is sitting at his desk at work an image of harming his young son pops into his mind. Each time this occurs, he touches all four corners of his desk in a particular order. Sid probably suffers from

Why do African Americans have an elevated risk for developing sickle-cell anemia?

a) Their diet is conducive to the disease. b) They have very high levels of oxygen in the blood. c) They are prone to produce elevated amounts of cholesterol. d) They are more likely to carry the recessive gene for the disease.

What exciting event occurs first during the second trimester of a pregnancy?

A) Morning sickness eases B) The first visit to the obstetrician C) First sensations of fetal movement D) Couples can start having sex again