精题分解：2010届高考各地模拟阅读理解分类汇编（5）
（复习类）55篇
世纪金榜www.jb1000.com
医学保健类
1
（江苏省六合高级中学2010届高三第一次调研考试）
Happiness is genetic
HAPPINESS and sadness are states of being that define the way we view the world. It is often said that some people by nature have a sunny disposition（性格）. Now scientists may have discovered why.
Some people may be hard-wired（天生的）for happiness, while others are genetically negative, scientists have suggested in a study published late February, in British journal Proceedings of the Royal Society B（《皇家学会学报B》）.
Earlier research had already established that the gene known as 5-HTTLPR plays a key role in determining how the neurotransmitter（神经传递素）serotonin（含于血液中的复合胺）works within the brain. Serotonin, a hormone（荷尔蒙）, passes chemical messages between nerve cells. It has been closely linked to mood. Several anti-depressant（抗抑郁）drugs regulate serotonin levels.
