染色體終端位於每一條真核染色體兩端，可提供染色體穩定，其結構是由一再重複的核甘酸序列及一些蛋白質組成的。染色體終端長度與細胞壽命有關。人體淋巴球之染色體終端長度，隨年齡增加而長度減少。智能不足的病人，定義為智力較正常人低下，或適應能力較一般人低下， 智商(IQ)在70以下。人類的智商在30-34歲達最高，之後逐漸下降。預期壽命(Life expectancy)定義為個體剩下的存活時間，增加預期壽命表示個體壽命增加。智能不足預期壽命一般較普通人短。本實驗之目的在探討正常組之智商與染色體終端長之相關性及智能不足病人之染色體終端長度是否較正常組短。取智能不足之病人59位，根據精神疾病診斷及統計手冊第四版(DSM-IV)依病情分成輕度、中度、重度、極重度四級，另外以年齡在19-21歲之護校女生共52位為對照組。抽血並從淋巴球中萃取DNA，以南方墨點法分析染色體終端DNA，再以軟體分析其長度。統計方面以Pearson積差相關求取正常組之智商(IQ; 含PIQ, VIQ, TIQ)與染色體終端長度是否有相關；再以單因子變異數分析(one-way ANOVA)檢定各組（正常組、輕度、中度、重度、極重度智能不足）之染色體終端長度是否有顯著差異。分析結果顯示，正常組(N=52)之染色體終端長度與PIQ(r=-0.001; p=0.922)、VIQ(r=-0.033; p=0.817)、TIQ(r=-0.026, p=0.857)無相關性存在；正常組、輕度、中度、重度、極重度智能不足五組間之染色體終端長度無顯著差異(F=0.0.859, p=0.491)，但有一位27歲個案其終端長度(4.135kb)遠低於其他個案之平均值(9.307kb).。因此在本實驗條件下，正常組及智能不足者之智能與淋巴球之終端長度並無統計學上之差異。從這個研究結果顯示，在良好環境下，智能不足者與一般人可有接近之預期壽命。

Telomeres are located at the ends of all eukaryotic chromosomes and provide the stability of chromosomes. They consist of simple tandem hexametric repeats and play an important part in cell longevity. In human lymphocytes, telomeres shorten progressively with age. Mental retardation (MR) is a disorder with intelligence quotient below average (IQ < 70) and impairment in adaptive skills. IQ by Weschsler Adult Intelligence Scales revised (WAIS-R) appears to peak in the of 30-34 and thereafter decline gradually. Life expectancy is defined as the number of years remaining to be lived. The overall increase in life expectancy indicates an improvement in longevity. The life expectancy of MR patients is shorter than that of the general population. The purpose of this study is to predict the relationship between telomere length and IQ in normal control as well as to analyze the differences among the average telomere length for the control and subgroups of MR cases. Fifty-nine patients who met the fourth edition of Diagnostic and Statistical Manual of Mental Disorders (DSM-IV) criteria for mental retardation were included in this study. According to the degree of intellectual impairment, MR patients were divided into 4 types: mild, moderate, severe, and profound. Fifty-two female nursing students aged 19-21 were recruited as normal controls. DNA was isolated from their lymphocytes. Telomere length was analyzed by Southern blot hybridization. The length was calculated by the Photo CaptMw Version 99.03 software. Correlation between the telomere length and IQ in normal control was performed by the Pearson product-moment correlation. One-way ANOVA was used to test if any differences existed among the normal, mild, moderate, severe, and profound MR. Analyses displayed that there were no correlations between telomere length and IQ including PIQ(r=-0.001; p=0.922), VIQ(r=-0.033; p=0.817), TIQ(r=-0.026, p=0.857), and no difference existed among the normal and subgroups of MR cases. Results obtained from this study indicated that life expectancy of MR patients may approximate to that of the general population if live in the well environment.

CONTENTS
中文摘要…………………………………….……….…4

ABSTRACT…..……..………….…..……….………..…6

INTRODUCTION…….………………..…...……….….8

MATERIALS AND METHODS……...……....…....….13

RESULTS…………………….….………...………..….18

DISCUSSION………..………………...……..…….….20

REFERENCES……………………..…………....…….25

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