Bargiello T A, Jackson F R, Young M W
Nature. 1984;312(5996):752-4. doi: 10.1038/312752a0.
The per locus of Drosophila melanogaster has a fundamental role in the construction or maintenance of a biological clock. Three classes of per mutations have been identified: per mutants have circadian behavioural rhythms with a 29-h rather than a 24-h period, pers mutants have short-period rhythms of 19 h, and per mutants have no detectable circadian rhythms. Each of these mutations has a corresponding influence on the 55-s periodicity of male courtship song. Long- and short-period circadian rhythm phenotypes can also be obtained by altering the dosage of the wild-type gene: for example, females carrying only one dose of this X-linked gene have circadian rhythms with periodicities about 1 h longer than those carrying two doses. In a previous report, cloned DNA was used to localize several chromosomal rearrangement breakpoints that alter per locus function. The rearrangements all affected a 7-kilobase (kb) interval that encodes a 4.5-kb poly(A)+ RNA. We report here that when a 7.1-kb fragment from a per+ fly, including the sequences encoding the 4.5-kb transcript, is introduced into the genome of a per (arrhythmic) fly by P element-mediated transformation, circadian rhythmicity of behaviour such as eclosion and locomotor activity is restored. The transforming DNA complements per locus deletions and is transcribed, forming a single 4.5-kb poly(A)+ RNA comparable to that produced by wild-type flies.
果蝇的周期基因（per locus）在生物钟的构建或维持中起着重要作用。已鉴定出三类周期基因突变：周期突变体（per mutants）具有29小时而非24小时周期的昼夜行为节律，短周期突变体（pers mutants）具有19小时的短周期节律，而无节律突变体（per mutants）则没有可检测到的昼夜节律。这些突变中的每一种对雄蝇求偶歌的55秒周期都有相应影响。通过改变野生型基因的剂量也可以获得长周期和短周期的昼夜节律表型：例如，仅携带一份这种X连锁基因的雌性果蝇的昼夜节律周期比携带两份该基因的雌性果蝇长约1小时。在之前的一份报告中，利用克隆DNA定位了几个改变周期基因功能的染色体重排断点。这些重排均影响了一个7千碱基（kb）的区间，该区间编码一种4.5 kb的多聚腺苷酸化（poly(A)+）RNA。我们在此报告，当来自野生型（per+）果蝇的一个7.1 kb片段（包括编码4.5 kb转录本的序列）通过P因子介导的转化引入无节律（per）果蝇的基因组时，羽化和运动活动等行为的昼夜节律得以恢复。转化DNA弥补了周期基因座的缺失并被转录，形成一种与野生型果蝇产生的4.5 kb多聚腺苷酸化（poly(A)+）RNA相当的单一RNA。
