📖 基因：说明书里的一个个条目📖 Genes: entries in the instruction manual
上一片看到了 DNA 双螺旋——生命的梯子。这一片来认识梯子上一个个有名字的段落：基因。Last leaf we saw the DNA double helix — life's ladder. This leaf meets the named sections written on it: genes.
第 1 步：说明书里的一个条目Step 1: One entry in the manual
先解决一个疑问：DNA 那么长，细胞怎么知道哪一段管什么？First a puzzle: DNA is enormous — how does a cell know which stretch does what?
DNA 像一卷超长的说明书，30 亿个字母一路写下去。一个基因，就是说明书里被标出来的一个条目——通常几百到几万个字母，只负责一件事。人有大约 2 万个基因条目。DNA is one gigantic instruction manual, 3 billion letters long. A gene is a marked entry in that manual — a few hundred to tens of thousands of letters, in charge of one job. Humans have about 20,000 gene entries.
条目只是一行指令，它不会自己动手。那指令交给谁去执行？An entry is only an order — it can't do work by itself. Who carries it out?
第 2 步：一条流水线：基因 → 蛋白质 → 性状Step 2: One assembly line: gene → protein → trait
基因的指令先被抄成一张工单，送去造蛋白质。蛋白质是细胞里的工人：搭肌肉、开通道、发信号。耳垂基因造出耳垂塑形蛋白，耳朵就长成该有的样子——指令（基因）变成工人（蛋白质），最后变成看得见的结果（性状）。The gene's order is copied into a work ticket and sent out to build a protein. Proteins are the cell's workers: they build muscle, open channels, send signals. The earlobe gene builds an earlobe-shaping protein, and the ear grows the way it should — an order (gene) becomes a worker (protein), and finally a visible result (trait).
只有 2 万个条目，怎么写出几十万亿个细胞、几十亿个不一样的人？Just 20,000 entries — how do they write trillions of cells and billions of different people?
第 3 步：两万条指令，版本各不同Step 3: 20,000 orders, many versions
同一条目人人都有，但版本可能不同：有人有耳垂、有人没有；有人能卷舌、有人不能；有人成年后喝奶难受、有人没事；有人觉得西兰花苦、有人觉得不苦。所以“天赋基因检测”说能算出你擅长什么，其实远没那么神——基因给的是倾向，不是命运，环境和练习也在写这本书。Everyone has the same entries, but the versions differ: some earlobes attach, some don't; some can roll their tongues; some find milk uncomfortable as adults; some taste broccoli as bitter. So “talent gene tests” that claim to predict what you'll be good at are far from magic — genes offer tendencies, not destiny; environment and practice write the book too.
🦠 你来接通流水线（30 秒）🦠 Your turn: connect the line (30 seconds)
点开基因卡，先选它造出的蛋白质，再选它带来的性状——4 条流水线全接通就通关。Open each gene card, pick the protein it builds, then the trait it brings — connect all 4 lines to win.
一句话记住它：基因 = DNA 上管一件事的一个条目；基因造蛋白质，蛋白质带来性状。Remember it in one line: a gene is one entry in the DNA manual, in charge of one job; genes build proteins, and proteins bring traits.
基因是 DNA 上的功能片段，一个基因管一件事，人有约 2 万个A gene is a working stretch of DNA — one gene, one job; humans have ~20,000流水线：基因（指令）→ 蛋白质（工人）→ 性状（结果）The line: gene (order) → protein (worker) → trait (result)耳垂、卷舌、喝奶、苦味这些差异，是同一条目的不同版本；检测给的是倾向，不是命运Earlobes, tongue rolling, milk, bitterness — versions of the same entries; tests give tendencies, not destiny
内容参考 OpenStax 等公开教材，多来源核对 · AI 生成、人工审核 · 发现错误欢迎指正，帮这片叶子长得更好。Based on OpenStax and other open textbooks, cross-checked across sources · AI-generated, human-reviewed · Spotted a mistake? Tell us — help this leaf grow.
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