《那些古怪又讓人憂心的問題》第70期:自體繁殖(4)
Humans
人類
In humans, probably the most common genetic disorder caused by inbreeding is spinal muscular atrophy (SMA). SMA causes the death of the cells in the spinal cord, and is often fatal or severely disabling.
在人類中，由近親繁殖帶來的最普遍的遺傳缺陷可能是脊髓性肌肉萎縮症。這種疾病會導致脊髓中的細胞死亡，最後可能會致命或造成嚴重殘疾。SMA is caused by an abnormal version of a gene on chromosome 5. About 1 in 50 people have this abnormality, which means 1 in 100 people will contribute it to their children . . . and, therefore, 1 in 10,000 people (100 times 100) will inherit the defective gene from both parents.
脊髓性肌肉萎縮症是由5號染色體上的一個基因異常造成的。平均每50人中就會有一個人的這個基因出現異常，這意味着每100個人就會有一個人把它遺傳給他們的孩子……因而每1萬人（100×100）中，就會有一個人從父母那裏都繼承到這種有缺陷的基因。
If a parent has a child with his- or herself, on the other hand, the chance of SMA is 1 in 400-since if he or she has a copy of the defective gene (1 in 100), there's a 1 in 4 chance it will be the child's only copy.
如果一個人打算自體繁殖，那麼得病的機率爲四百分之一——他自己有這種缺陷基因的機率是百分之一，而又有四分之一的機率他的孩子只會繼承到這個基因。One in 400 may not sound so bad, but SMA is only the start.
四百分之一的機率聽起來還不算太糟糕，但這僅僅是個開始。DNA is complicated
複雜的DNADNA is source code for the most complex machine in the known universe. Each chromosome contains a staggering amount of information, and the interaction between DNA and the cell machinery around it is incredibly complicated, with countless moving parts and Mousetrap-style feedback loops. Even calling DNA “source code” sells it short-compared to DNA, our most complex programming projects are like pocket calculators.
DNA是宇宙中已知的最複雜機械的源代碼。每一條染色體上都包含巨量的信息。而DNA和周圍細胞工廠的相互作用又極其複雜，包含了無數的移動部件和捕鼠器式的反饋循環。甚至把DNA稱作源代碼都太小看它了。與DNA相比，我們最複雜的編程項目看起來就像便攜式計算器那樣簡單。In humans, each chromosome affects many things through a variety of mutations and variations. Some of these mutations, like the one responsible for SMA, seem to be entirely negative; the mutation responsible has no benefit. In our D&D system, it's like a chromosome having an STR of 1. If your other chromosome is normal, you'll have a normal character stat; you'll be a silent “carrier.”
在人體中，每條染色體通過一系列的突變和變異影響着許多其他的東西。其中一些突變，就像造成脊髓性肌肉萎縮症的那個突變，產生的結果完全是負面的，這種基因突變是沒有益處的。在《龍與地下城》系統中，它就像力量值爲1的染色體，如果你的其他染色體都是正常的，那麼你的整體屬性值也將會是正常的，但你是一個隱形的“攜帶者”。Other mutations, like the sickle-cell gene on chromosome 11, can provide a mix of benefit and harm. People who have the sickle-cell gene on both their copies of the chromosome suffer from sickle-cell anemia. However, if they have the gene on just one of their chromosomes, they get a surprise benefit: extra resistance to malaria.
其他的突變，比如11號染色體上鐮狀紅細胞基因，既會帶來好處也會帶來壞處。如果一個人的兩條遺傳序列上都有鐮狀紅細胞基因，那麼他們就會得鐮狀紅細胞貧血症；如果他們只有一條遺傳序列上有這種基因，就會產生一個意料之外的好處：對瘧疾的額外免疫性。
