Final answer:
Scientists have used identical twins as research subjects to study the effects of long-term space travel on the human body.
Step-by-step explanation:
Before his flight to space, the genetic sample technician shared with Vincent that scientists have used identical twins as research subjects to study the effects of long-term space travel on the human body. In this case, Mark Kelly, one of the twin astronauts, spent almost a full year on the International Space Station, while his twin Scott Kelly served as a control on the ground. By comparing their health data and nutritional indicators, NASA is able to learn about the impact of space travel on the human body.
The provided information about identical twins and their use in scientific studies pertains to the Kelly brothers, Mark and Scott. NASA used their twin status to understand the health effects of long-term space travel by comparing data taken from them during and after Mark Kelly's stay on the International Space Station (ISS).