Bastié-Sigeac F, Lucotte G
Hum Genet. 1983;63(2):162-5. doi: 10.1007/BF00291537.
Numerous biological factors have an effect upon the probability of the presence of a theoretical restriction site at a given point, (1/4)n, in a DNA molecule, where n represents the number of base pairs composing the site. Indeed, it is a fact that the ratio (formula; see text) does not usually equal unity. In addition, the sequence of the nucleotides appears to change haphazardly, with certain dinucleotides present more often than others. When considering (formula; see text), it is observed that the influence of this first parameter is very important for sites with either four or six base pairs. The balance of the average frequency of each site according to the preponderance of certain dinucleotides and the G + C content has been the subject of an involved study which makes use of a certain number of restriction enzymes which are commercially available. The important frequency variations of different sites are due primarily to the presence of one or two GC doublets which go as far as reducing the frequency by a factor of 3.
许多生物学因素会影响在DNA分子中给定位置（1/4）ⁿ处存在理论限制位点的概率，其中n表示构成该位点的碱基对数量。实际上，（公式；见原文）这个比率通常不等于1是一个事实。此外，核苷酸序列似乎是随机变化的，某些二核苷酸比其他二核苷酸出现得更频繁。在考虑（公式；见原文）时，可以观察到这个第一个参数对具有四个或六个碱基对的位点的影响非常重要。根据某些二核苷酸的优势和G + C含量来平衡每个位点的平均频率，这是一项涉及使用一定数量市售限制酶的复杂研究的主题。不同位点重要的频率变化主要是由于存在一个或两个GC双峰，这甚至会使频率降低3倍。
