After examining the gene cyp2a6 among 300 smokers and those who had smoked in the past , the scientists found that 70 percent of those with a highly active type of the gene were highly addicted to nicotine . the percentage of heavy smokers among those with a less active cyp2a6 was lower at 40 percent , the finding showed 本次研究所涉及的对象包括300名正在吸烟者以及一些从前曾经吸过烟的人,科学家们对这些人体内一个名叫cyp2a6的基因进行了相关的检测,结果显示,在那些该基因表现得异常活跃的人里,对尼古丁高度成瘾者所占的比例为70 % 。