📚 Cloning Biotechnology Practice Questions | 克隆生物技术 真题精练
Welcome to this focused revision resource on cloning and biotechnology. This article combines key topic summaries with carefully designed examination-style questions. Each question is accompanied by bilingual explanations that mirror the depth required for top grades. Use these materials to consolidate your understanding and sharpen your exam technique.
欢迎来到克隆与生物技术专项复习资源。本文结合关键知识点总结与精心设计的真题风格练习。每道题目都配有深度契合高分要求的双语解析。通过这些材料巩固理解，磨炼应试技巧吧。
1. Core Concepts of Cloning | 克隆的核心概念
Cloning is the production of genetically identical organisms or cells from a single parent. In nature, asexual reproduction and mitosis already produce clones, but modern biotechnology allows scientists to clone plants and animals artificially. The term 'clone' can refer to a whole organism, tissues, or even DNA fragments.
克隆是指从一个亲本产生遗传完全相同的生物体或细胞的过程。在自然界中，无性繁殖和有丝分裂已经能产生克隆，但现代生物技术使科学家能够人工克隆动植物。术语“克隆”可以指完整生物、组织甚至DNA片段。
In A‑level specifications, two main forms of cloning are emphasised: reproductive cloning, which creates identical whole organisms, and therapeutic cloning, which produces embryonic stem cells for medical treatments. Understanding the distinction is vital for evaluating ethical debates.
在A‑level考纲中，强调两种主要的克隆形式：生殖性克隆（产生相同的完整生物体）和治疗性克隆（产生用于医疗的胚胎干细胞）。理解这一区别对评估伦理辩论至关重要。
2. Plant Tissue Culture | 植物组织培养
Plant tissue culture is a method of cloning plants from small pieces of tissue called explants. The explant is sterilised and placed on a sterile nutrient agar medium containing auxins and cytokinins. Under aseptic conditions, the cells divide by mitosis to form a callus, an undifferentiated mass of cells.
植物组织培养是从称为外植体的小块组织中克隆植物的方法。外植体经消毒后，放置在含有生长素和细胞分裂素的无菌营养琼脂培养基上。在无菌条件下，细胞通过有丝分裂形成愈伤组织——一团未分化的细胞团。
The callus can be subdivided and transferred to a fresh medium with a different hormone balance to stimulate shoot and root development. Eventually, many identical plantlets are produced, which can be potted into soil. This technique is widely used in horticulture and crop improvement.
愈伤组织可被切分并转移到含不同激素配比的新鲜培养基上，以刺激茎叶和根的发育。最终产生许多相同的植株，可移栽入土。这项技术广泛用于园艺和作物改良。
- Auxin promotes root formation; cytokinin promotes shoot growth.
- 生长素促进根的形成；细胞分裂素促进茎叶生长。
- Aseptic technique prevents contamination by bacteria and fungi.
- 无菌操作防止细菌和真菌污染。
3. Micropropagation in Detail | 微体繁殖详解
Micropropagation is an industrial application of plant tissue culture that allows rapid multiplication of disease‑free stock plants. It involves four stages: initiation, multiplication, rooting, and acclimatisation. During the multiplication stage, cytokinin‑rich medium encourages the formation of multiple shoots from a single explant.
微体繁殖是植物组织培养的工业应用，可快速增殖无病母株。它包含四个阶段：启动、增殖、生根和驯化。在增殖阶段，富含细胞分裂素的培养基促使单个外植体形成多个茎芽。
Micropropagation offers significant advantages: thousands of uniform plants can be produced year‑round in limited space, endangered species can be conserved, and pathogen‑free stocks can be continuously maintained. However, it is labour‑intensive and technically demanding.
微体繁殖具有显著优势：可在有限空间内全年生产数千株均一植株，可保护濒危物种，并能持续维护无病原体母株。然而，它劳动密集且技术要求高。
| Stage / 阶段 | Key activity / 关键活动 | Hormone emphasis / 激素侧重 |
|---|---|---|
| Initiation / 启动 | Explant sterilisation and placement on medium / 外植体消毒并置于培养基 | Balanced auxin and cytokinin / 生长素与细胞分裂素平衡 |
| Multiplication / 增殖 | Shoot proliferation / 茎芽增殖 | High cytokinin / 高细胞分裂素 |
| Rooting / 生根 | Induction of roots / 诱导生根 | High auxin / 高生长素 |
| Acclimatisation / 驯化 | Transfer to soil and gradual hardening / 移入土壤并逐渐炼苗 | No added hormones / 不添加激素 |
4. Somatic Cell Nuclear Transfer (SCNT) | 体细胞核移植
SCNT is the technique used to create Dolly the sheep. The nucleus is removed from an unfertilised egg cell (enucleation), and a somatic cell nucleus from the adult animal to be cloned is inserted. An electric shock stimulates the reconstructed cell to divide by mitosis, forming an embryo.
SCNT是用于创造克隆羊多莉的技术。从去核的未受精卵细胞中移除细胞核，然后插入待克隆成年动物的体细胞核。电击刺激重组细胞通过有丝分裂分裂，形成胚胎。
The embryo is then implanted into the uterus of a surrogate mother. The resulting offspring is genetically identical to the donor of the nucleus, except for mitochondrial DNA, which comes from the egg donor. SCNT has low success rates and may produce animals with health problems due to incomplete epigenetic reprogramming.
随后将胚胎植入代孕母亲的子宫。除线粒体DNA来自卵子供体外，由此产生的后代与细胞核供体遗传完全相同。SCNT成功率低，可能因表观遗传重编程不完整而产生健康问题的动物。
- Enucleated egg + somatic nucleus → reconstructed cell → embryo.
- 去核卵 + 体细胞核 → 重组细胞 → 胚胎。
- Mitochondrial DNA is inherited from the egg donor, not the nuclear donor.
- 线粒体DNA遗传自卵子供体，而非细胞核供体。
5. Embryo Splitting and Artificial Twinning | 胚胎分割与人工双生
Embryo splitting is a form of cloning that mimics natural monozygotic twinning. At an early stage (e.g., 8‑cell or blastocyst), an embryo is divided into two or more separate groups of cells. Each group can develop into a genetically identical individual if implanted into a uterus.
胚胎分割是一种模拟自然同卵双生的克隆形式。在早期阶段（如8细胞或囊胚期），将胚胎分成两个或多个独立的细胞群。若植入子宫，每一群均可发育成遗传相同的个体。
This method is simpler than SCNT and does not require enucleation or electrical fusion. However, it cannot produce clones from adult animals—it only works with embryos. Embryo splitting is used in cattle breeding to multiply elite embryos, but is rarely used in humans for ethical reasons.
这种方法比SCNT简单，无需去核或电融合。但它不能从成年动物克隆，只能使用胚胎。胚胎分割应用于牛育种中以扩增优良胚胎，但因伦理原因很少用于人类。
6. Therapeutic Cloning and Stem Cells | 治疗性克隆与干细胞
Therapeutic cloning uses SCNT to produce an embryo that is not implanted but cultured in vitro to the blastocyst stage. From the inner cell mass, embryonic stem cells are harvested. These pluripotent cells can differentiate into any cell type, offering potential for regenerative medicine.
治疗性克隆利用SCNT产生胚胎，但该胚胎不植入子宫，而是在体外培养至囊胚阶段。从内细胞团获取胚胎干细胞。这些多能干细胞可分化成任何细胞类型，为再生医学带来潜力。
Because the stem cells share the patient's DNA, there is no risk of immune rejection. However, the destruction of the embryo raises significant ethical objections. Some countries permit therapeutic cloning under strict regulation, while others ban it entirely.
由于干细胞与患者共享DNA，因而无免疫排斥风险。然而，胚胎的破坏引发了重大伦理异议。一些国家在严格法规下允许治疗性克隆，而另一些国家则完全禁止。
- Pluripotent stem cells can form any foetal tissue but not extra‑embryonic tissues.
- 多能干细胞可形成任何胎儿组织，但不能形成胚外组织。
- Induced pluripotent stem cells (iPSCs) are an alternative produced by reprogramming adult somatic cells, avoiding embryo use.
- 诱导多能干细胞(iPSCs)是通过重编程成体细胞获得的替代方案，避免使用胚胎。
7. Ethical and Social Dimensions | 伦理与社会维度
Ethical considerations surrounding cloning include concerns about animal welfare, human dignity, and the 'commodification' of life. In reproductive cloning, the low efficiency and high incidence of abnormalities in cloned animals raise serious welfare issues. Many people worry that applying SCNT to humans would be unnatural and could lead to psychological harm for the cloned individual.
围绕克隆的伦理考量包括对动物福利、人类尊严以及生命“商品化”的担忧。在生殖性克隆中，克隆动物效率低下且异常率较高，引发了严重的福利问题。许多人担心将SCNT应用于人类是不自然的，可能对克隆个体造成心理伤害。
Therapeutic cloning triggers debate because it requires the creation and destruction of human embryos. Some argue that the potential life‑saving benefits justify the practice, while others believe the embryo has moral status from conception and should be protected. Legislation varies widely around the world.
治疗性克隆引发争论，因为它需要制造并摧毁人类胚胎。一些人认为其潜在的救命益处足以证明其正当性，而另一些人则认为胚胎自受孕起便具有道德地位，应受保护。世界各地立法差异很大。
8. Practice Question Set 1: Plant Cloning | 真题练习一：植物克隆
Question 1: A gardener wants to produce a large number of virus‑free orchids from a rare parent plant. Outline the steps of micropropagation and explain why aseptic technique is critical. (4 marks)
题目1：一位园艺师希望从一株稀有母株中大量繁殖无病毒兰花。概述微体繁殖的步骤，并解释为何无菌操作至关重要。（4分）
Question 2: During tissue culture, the medium contains the hormones auxin and cytokinin. Describe how changing the ratio of these hormones influences the development of explants. (3 marks)
题目2：在组织培养中，培养基含有生长素和细胞分裂素。描述改变这两种激素比例如何影响外植体的发育。（3分）
Question 3: Micropropagation can produce thousands of identical plants. Suggest one biological advantage and one potential ecological risk of widespread planting of clonally identical crops. (2 marks)
题目3：微体繁殖能产生数千株相同植株。提出广泛种植克隆相同作物的一个生物学优势和一个潜在生态风险。（2分）
9. Practice Question Set 2: Animal Cloning and Ethics | 真题练习二：动物克隆与伦理
Question 4: Dolly the sheep was produced by somatic cell nuclear transfer (SCNT). Summarise the key steps, and explain why Dolly was not genetically 100% identical to the nuclear donor. (5 marks)
题目4：多莉羊通过体细胞核移植(SCNT)产生。总结关键步骤，并解释为何多莉与细胞核供体在遗传上并非100%相同。（5分）
Question 5: Compare embryo splitting and SCNT as methods of animal cloning, highlighting one advantage and one disadvantage of each. (4 marks)
题目5：比较胚胎分割和SCNT作为动物克隆方法，各指出一个优点和一个缺点。（4分）
Question 6: 'Therapeutic cloning should be permitted because it could cure devastating diseases, but reproductive cloning should remain banned.' Discuss the ethical arguments supporting and opposing this statement. (6 marks)
题目6：“应允许治疗性克隆，因为它能治愈毁灭性疾病，但生殖性克隆应保持禁止。”讨论支持和反对这一论述的伦理论点。（6分）
10. Model Answers and Explanations for Set 1 | 练习一参考答案与解析
Answer to Question 1: Explant taken from the orchid and surface‑sterilised; placed on sterile nutrient agar with plant hormones; cells divide to form callus; callus transferred to shoot‑inducing medium, then root‑inducing medium; plantlets potted into soil. Aseptic technique is crucial to prevent bacterial and fungal contamination which would compete for nutrients and release toxins, killing the cultured cells. (Award marks for correct sequence and clear explanation of contamination consequences.)
题目1答案：从兰花取外植体并表面消毒；放于含植物激素的无菌营养琼脂上；细胞分裂形成愈伤组织；愈伤组织转移至促芽培养基，再至促根培养基；小植株移栽入土。无菌操作至关重要，可防止细菌和真菌污染，避免其竞争养分并释放毒素杀死培养细胞。（评分点：步骤顺序正确，以及清楚解释污染后果。）
Answer to Question 2: A high cytokinin to auxin ratio promotes shoot formation and bud multiplication. A high auxin to cytokinin ratio stimulates root development. An approximately equal ratio favours callus maintenance. Changing the ratio allows selective control over organogenesis in the explant. (3 marks for linking ratio to outcome.)
题目2答案：高细胞分裂素与生长素比例促进芽形成和芽增殖。高生长素与细胞分裂素比例刺激根发育。大致相等的比例有利于维持愈伤组织。改变比例可选择性地控制外植体中的器官发生。（3分：联系比例与结果。）
Answer to Question 3: Biological advantage – all plants have uniform desirable traits (e.g., flower colour, disease resistance). Ecological risk – genetic uniformity makes the whole crop susceptible to the same pathogen or environmental change, increasing the chance of catastrophic failure. (2 marks, one each.)
题目3答案：生物学优势——所有植株具有统一优良性状（如花色、抗病性）。生态风险——遗传均一性使整个作物易受同一病原体或环境变化的影响，增加灾难性失败可能。（2分，各1分。）
11. Model Answers and Explanations for Set 2 | 练习二参考答案与解析
Answer to Question 4: Key steps: (i) Enucleate a donor egg cell; (ii) Insert the nucleus from a somatic cell of the adult sheep to be cloned; (iii) Electric shock to fuse and stimulate cell division; (iv) Culture to early embryo; (v) Implant into surrogate. Dolly was not 100% identical because mitochondrial DNA comes from the egg donor, not the nuclear donor. Also epigenetic reprogramming may differ. (5 marks: 1 mark per step, plus explanation of mitochondrial inheritance.)
题目4答案：关键步骤：(i)去核供体卵细胞；(ii)插入待克隆成年绵羊的体细胞核；(iii)电击融合并刺激细胞分裂；(iv)培养至早期胚胎；(v)植入代孕母体。多莉并非100%相同，因为线粒体DNA来自卵子供体而非细胞核供体。此外表观遗传重编程可能不同。（5分：每步1分，加上线粒体遗传解释。）
Answer to Question 5: Embryo splitting: advantage – technically simpler, no need for enucleation or electric fusion; disadvantage – only works with embryos, cannot clone an adult with known traits. SCNT: advantage – can clone an adult animal with proven desirable characteristics; disadvantage – very low efficiency, high rate of developmental abnormalities. (4 marks: one advantage and one disadvantage each.)
题目5答案：胚胎分割：优点——技术更简单，无需去核或电融合；缺点——仅适用于胚胎，无法克隆具有已知性状的成年个体。SCNT：优点——可克隆具有验证优良特性的成年动物；缺点——效率极低，发育异常率高。（4分：各一个优点一个缺点。）
Answer to Question 6: Arguments supporting therapeutic cloning include its potential to produce patient‑specific stem cells for treating Parkinson’s, diabetes, and spinal injuries without immune rejection. It may reduce reliance on organ donation. Arguments against include the destruction of human embryos, which some view as ending a potential human life. Opponents also warn about a slippery slope toward reproductive cloning and exploitation of women for eggs. The statement distinguishes between the two types, acknowledging medical benefits while upholding the prohibition on reproductive cloning. A balanced discussion should weigh the moral status of the embryo against the duty to relieve suffering, possibly mentioning iPSCs as an ethical alternative. (6 marks for reasoned evaluation covering both sides.)
题目6答案：支持治疗性克隆的论点包括其潜力，可制造患者特异性干细胞，用于治疗帕金森病、糖尿病和脊髓损伤，且无免疫排斥。这可能减少对器官捐献的依赖。反对论点包括摧毁人类胚胎，一些人视之为终结潜在人类生命。反对者还警告可能导致向生殖性克隆的滑坡以及为获卵而剥削女性。该论述区分了两种类型，承认医学益处同时坚持禁止生殖性克隆。平衡讨论应权衡胚胎的道德地位与减轻痛苦的义务，可能提及iPSCs作为伦理替代方案。（6分：涵盖两方的有理据评估。）
12. Key Terminology | 关键术语
Memorising precise terminology is essential for scoring full marks in structured questions. Below is a summary of high‑frequency terms you should be able to define and use in context.
熟记精确术语对于在结构化题目中获得满分至关重要。以下高频术语汇总，应能定义并在上下文中使用。
| Term / 术语 | Definition / 定义 |
|---|---|
| Clone | A genetically identical copy of an organism or cell. |
| Explant | A small piece of tissue removed from a parent plant for culture. |
| Callus | An undifferentiated mass of plant cells produced from explants. |
| SCNT | Somatic cell nuclear transfer; transferring a body cell nucleus into an enucleated egg. |
| Pluripotent | Able to give rise to any foetal cell type, but not extra‑embryonic tissues. |
| Therapeutic cloning | SCNT to produce embryos for harvesting stem cells, not for implantation. |
| Acclimatisation | Gradual adaptation of tissue‑cultured plantlets to external environment. |
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