In this Tuesday, April 25, 2017 photo, post doctoral fellow Leslie Mitchell, works at her bench at a New York University lab in the Alexandria Center for Life Sciences in New York, where researchers are attempting to create completely man-made, custom-built DNA. Mitchell says it took her a couple months to build her chromosome but longer to debug. &amp;#034;The tiniest change in the code can have dramatic effect on growth, she said. We are learning new rules about how cells operate by building from scratch.&amp;#034; (AP Photo/Mary Altaffer)