BehavioralGenetics

Behavioral Genetics,What is genetics?,Genetics is the study of heredity. Heredity is a biological process where a parent passes certain genes onto their children or offspring（后代）. Every child inherits genes from both of their biological parents and these genes in turn express specific traits（特性）.,-Part 1 What is behavioral genetics?,Human behavioral genetics, a relatively new field, seeks to understand both the genetic and environmental contributions to individual variations in human behavior.,The father of behavioral genetics,Sir Francis Galton(1822-1911) was the first scientist to study heredity and human behavior systematically. An explorer and anthropologist, Francis Galton is known for his pioneering studies of human intelligence. He devoted the latter part of his life to eugenics.,Francis Galton (弗朗西斯.高尔顿),However, the study of behavioral genetics is not an easy task, for the following reasons.,1）It often is difficult to define the behavior in question. Intelligence is a classic example. During the late summer of 1999,a Princeton molecular biologist(普林斯顿分子生物学家) published the results of an impressive research in which he enhanced the ability of mice to learn by inserting(嵌入) a gene that codes for a protein in brain cells known to be associated with memory.2)The investigator must measure the behavior with acceptable degrees of validity and reliability.,3)Behaviors, like all complex traits, involve multiple genes that complicates the search for genetic contributions.4)Studies of genes and behavior require analysis of families and populations for comparison of those who have the trait in question with those who do not.,-Part 2 What indications are there that behavior has a biological basis?,1)Behavior often is species specific.举个例子，山雀会衔着从饲养员那里得到的向日葵种子到一个安全的地方才会开始啄食，但是相反地，其他的雀类却会直接在饲养员面前啄食向日葵的种子。生物学家们利用这些不同来说明近缘物种间也存在行为差异。,2)Behaviors change in response to alterations in biological structures or processes.例如，脑部的损伤可以使一个人的行为与受伤前相比大相径庭。最近，遗传学家已经通过嵌入或提取特有基因来控制小白鼠的行为。,3)In humans, some behaviors run in families.精神一类的疾病在家族间有明显的遗传迹象。4)Behavior has an evolutionary history that persists across related species.黑猩猩与人类是亲缘最近的物种，DNA序列中只有2%的差异。人类与黑猩猩在行为特征方面都有很高的社会灵长性，包括繁衍、合作、利他甚至在面部表情上都很相似。,-Part 3 How is behavioral genetics studied?,Traditional research strategies in behavioral genetics include studies of twins and adoptees to sort biological from environmental influences.Recent research have added the pieces of DNA associated with particular behaviors.,Schizophrenia精神分裂症,精神分裂症(schizophrenia)是一种常见的精神病，据世界卫生组织估计，全球精神分裂症的终身患病率大概为3.8-8.4，多起病于青壮年，表现为感知、思维、情感、意志行为等多方面障碍，精神活动与周围环境和内心体验不协调，脱离现实。一般无意识障碍和明显的智能障碍，可有注意、工作记忆、抽象思维和信息整合等方面认知功能损害。病程多迁延，反复发作，部分患者发生精神活动衰退和不同程度社会功能缺损。,Bipolar disorder 双向情感障碍,双相障碍是一种常见的精神障碍。西方发达国家90年代流行病学调查显示，双相障碍终生患病率5.5%-7.8%。发病年龄高峰期15-19岁，首次多为抑郁发作，往往一至数次抑郁发作后再出现躁狂或轻躁狂发作。香港特区（1993）男性1.5%、女性1.6%。疾病危害：双相障碍如不治疗，易反复发作，长期的反复发作，导致患者疾病慢性化、人格改变和社会功能受损。由于病前的人格和疾病症状的影响，患者酒依赖、物质滥用、药物依赖发生率高。抑郁时由于情绪低落、悲观厌世可出现自伤自杀，自杀发生率高，激越时由于情绪极度烦躁，冲动控制能力弱，有可能出现伤人、毁物。,Downs syndrome 唐氏综合症,21-三体综合征，又称先天愚型或唐氏综合征，是小儿最为常见的由常染色体畸变性所导致的出生缺陷类疾病。顾名思义，该病是由先天因素造成的具有特殊表型的智能障碍。我国活产婴儿中21-三体综合征的发生率约为0.50.6，男女之比为32，60%的患儿在胎儿早期即夭折流产。患儿的主要临床特征为智能障碍、体格发育落后和特殊面容，并可伴有多发畸形。,21-三体综合征,-Part 4 What implications does behavioral genetics research have for society?,Researchers in the field of behavioral genetics have asserted claims for a genetic basis of numerous physical behaviors, including homosexuality, aggression, impulsivity, and nurturing.,There are several scientific obstacles to correlating genotype and behavior. 1) Defining a specific endpoint that characterizes a condition, be it schizophrenia or intelligence. 2) Identifying and excluding other possible causes of the condition.,-Part 5 How do genes influence behavior?,No single gene determines a particular behavior. Behaviors are complex traits involving multiple genes that are affected by a variety of other factors.FOR EXAMPLE,A study published in 1999 claimed that overexpression(超表达) of a particular gene in mice led to enhanced learning capacity(能力).What the press didnt mention was that the learning enhancements observed in this study were short-term, lasting only a few hours to a few days in some cases.,Genetic factors also can influence the role of certain environmental factors in the development of a particular trait.FOR EXAMPLE,A person may have a genetic varia