生物学
1866
植物杂交实验
性状以一个个离散、隐藏的单位代代相传，按简单的比例分离、隐没、又重现。
Choose your version
通过种豌豆、并仔细清点后代，一位修士发现：性状是以一个个细小、独立的「小包裹」传下去的——那就是我们今天所说的基因。
核心想法
过去人们以为，孩子的性状不过是父母的混合——把一株高的和一株矮的配在一起，就该得到一株中等高的。孟德尔耐心地培育了成千上万株豌豆，发现的却是另一回事。把一株高豌豆和一株矮豌豆杂交，下一代里每一株都是高的。「矮」并没有被混淡、也没有消失——它只是藏了起来。
再让这些植株繁育下去，「矮」又会在接下来的一代里冒出来，比例几乎恰好是每四株里有一株。正是这个工整的比例，泄露了秘密。每株植物，一定都携带着两条关于高矮的隐藏指令，分别来自父母，而它只把其中一条传下去。有些指令「声音响」（显性），有些「声音轻」（隐性）——而一条「轻」的指令，可以隐匿一代，再原封不动地重现。
它是如何诞生的
格雷戈尔·孟德尔，是布吕恩（今布尔诺）一所修道院里的修士兼教师。在那座花园里，他用了约八年时间，种下并亲手授粉了数以万计的豌豆，逐一追踪单个性状，像会计记账一样清点结果。1865 年，他把发现报告给当地的自然史学会，并于 1866 年发表。
然后——几乎没有任何回响。对那个年代的生物学家来说，这工作太「数学」了，于是无人问津，搁置了 34 年。直到 1900 年，三位植物学家各自独立地，撞上了同样的规则，又翻出了孟德尔那篇被遗忘的论文。而那时，他已去世十六年。
它为何重要
孟德尔发现了遗传的基本规则——性状以离散的单位传递，它们并不混合，而是按可预测的概率重新洗牌、再度现身。他那被同代人忽视的数豌豆工作，后来成了遗传学、以及由此生长出来的一切的基石——从作物育种，到对遗传病的预测。
一个可以想象的画面
想象每个亲本，就一种性状各握着两张牌，并随机地只发一张给孩子。「高」是一张抢眼的牌，只要在场就显出来；「矮」则是一张害羞的牌，唯有当孩子恰好拿到两张时，才会现身。让两个 Tt 的亲本各发一张牌，平均而言，每四个孩子里有三个显高、一个显矮。把所有组合摆出来，便是一格庞尼特方格——到下面试试看。
它的位置
达尔文已经表明，生命靠自然选择演化，却缺少一套遗传的机制——而「后代不过是父母的混合」这一流行想法，本会把任何新出现的变异稀释殆尽。孟德尔的「颗粒式」因子，正是那块缺失的拼图：它们整个地传下去，于是变异得以保留。数十年后，两套思想被熔合为「现代综合」，而孟德尔那抽象的因子，终于在 DNA 双螺旋中获得了一具身躯。
Original source text
引言与豌豆的选择
Experience of artificial fertilisation, such as is effected with ornamental plants in order to obtain new variations in colour, has led to the experiments which will here be discussed. The striking regularity with which the same hybrid forms always reappeared whenever fertilisation took place between the same species induced further experiments to be undertaken, the object of which was to follow up the developments of the hybrids in their progeny.
Those who survey the work done in this department will arrive at the conviction that among all the numerous experiments made, not one has been carried out to such an extent and in such a way as to make it possible to determine the number of different forms under which the offspring of hybrids appear, or to arrange these forms with certainty according to their separate generations, or definitely to ascertain their statistical relations.
The selection of the plant group for experiments of this kind must be made with all possible care if it be desired to avoid from the outset every risk of questionable results. The experimental plants must necessarily possess constant differentiating characters, and their hybrids must be protected from the influence of all foreign pollen during the flowering period. The genus Pisum was found to possess the necessary qualifications.
显性与隐性性状
The characters which were selected for experiment relate to the form of the ripe seed (round or wrinkled); the colour of the seed albumen (yellow or green); the length of the stem (tall or dwarf); and four others — seven differentiating characters in all, each appearing in two clear, non-blending forms.
Those characters which are transmitted entire, or almost unchanged in the hybridisation, and therefore in themselves constitute the characters of the hybrid, are termed the dominant, and those which become latent in the process recessive.
The expression “recessive” has been chosen because the characters thereby designated withdraw or entirely disappear in the hybrids, but nevertheless reappear unchanged in their progeny. Transitional forms were not observed in any experiment.
第一代与第二代：3∶1
In the first generation from the crossing, every hybrid plant displays the dominant character, and the recessive form escapes observation completely. It is, moreover, perfectly immaterial whether the dominant character belongs to the seed-bearer or to the pollen-parent; the form of the hybrid is identical in both cases.
In this generation there reappear, together with the dominant characters, also the recessive ones with their peculiarities fully developed, and this occurs in the definitely expressed average proportion of three to one, so that among each four plants of this generation three display the dominant character and one the recessive.
Of 8023 seeds from one experiment, 6022 were yellow and 2001 green — a ratio of 3.01 to 1. In another, of 7324 seeds, 5474 were round and 1850 wrinkled — 2.96 to 1. The whole of the experiments yielded the average ratio 2.98 to 1.
2∶1∶1 的拆解
Those forms which in the next generation again breed true to the dominant character are revealed to be of two kinds. The dominant offspring are not uniform: one third of them breed true, while two thirds behave as hybrids — themselves splitting 3 : 1 in the generation that follows.
The relation of three to one, in which the distribution of the dominant and recessive characters results in the first generation, resolves itself therefore in all experiments into the proportion of 2 : 1 : 1 if at the same time the dominant character be distinguished according to its significance as a hybrid-character or as a parental one.
组合的法则
Pea hybrids form germinal and pollen cells which, in their composition, correspond in equal numbers to all the constant forms resulting from the combination of the characters united in fertilisation. The behaviour of each pair of differentiating characters in hybrid union is independent of the other differences in the two original parental stocks.
It is now clear why, in a hybrid plant, the differentiating characters can re-emerge in their parental purity: each germ cell and each pollen cell carries only one of the two. The constancy of the offspring, and the definite numerical ratios in which the forms appear, follow of necessity.
Read at the meetings of February 8 and March 8, 1865