 Rowan Chapman, at Natera NASDAQ:NTRA, made a large buy and sell of company shares on September 17, according to a new SEC filing. What Happened: A Form 4 filing from the U.S. Securities and Exchange Commission states that Rowan Chapman exercised options to purchase 5,500 Natera shares at a price of 32.15 per share for a total of 176,825 on September 17. 