Chinese scientists cloned two identical long tailed macaque monkeys using a laboratory method that involved transferring the nucleus of a body cell into an enucleated egg cell. By which cloning process was this achieved?

Introduction / Context:
Cloning of mammals such as sheep, cats and now monkeys has usually relied on specific nuclear transfer techniques. One famous method, used to create Dolly the sheep, is called somatic cell nuclear transfer. In this approach, the nucleus of a differentiated body cell is placed into an egg cell whose own nucleus has been removed. Chinese scientists used a similar strategy to clone two identical long tailed macaques. This question asks you to identify the correct name of the cloning process used.

Given Data / Assumptions:

• The cloned animals were long tailed macaque monkeys, a type of primate.
• The description refers to transferring a nucleus from a body (somatic) cell into an enucleated egg cell.
• Polymerase chain reaction is a molecular technique for amplifying DNA, not a whole animal cloning method.
• Parthenogenesis is development of an egg without fertilisation, and embryonic cell nuclear transfer uses embryonic nuclei rather than differentiated somatic nuclei.

Concept / Approach:
Somatic cell nuclear transfer is a cloning technique where the nucleus from a somatic (non reproductive) cell is inserted into an egg cell that has had its own nucleus removed. The reconstructed egg is then stimulated to divide and develop into an embryo, which can be implanted into a surrogate mother. This method produces an animal genetically almost identical to the donor of the somatic nucleus. Polymerase chain reaction is used instead to create many copies of a DNA segment. Parthenogenesis involves egg development without fertilisation and does not require nuclear transfer, and embryonic cell nuclear transfer uses nuclei from embryonic cells rather than from fully differentiated somatic cells. The reports on cloned macaques specifically mention somatic cell nuclear transfer as the approach used.

Step-by-Step Solution:
Step 1: Identify that the question describes a process where a nucleus from a body cell is transferred into an enucleated egg cell. Step 2: Recall that such a process is characteristic of somatic cell nuclear transfer, a technique used for cloning whole animals. Step 3: Consider option a, polymerase chain reaction, and remember that this is a DNA amplification method used in test tubes, not an embryo cloning method. Step 4: Consider option b, parthenogenesis, which involves an egg developing without fertilisation but does not involve nuclear transfer from a somatic cell. Step 5: Distinguish option c, somatic cell nuclear transfer, from option d, embryonic cell nuclear transfer, and select somatic cell nuclear transfer because the question emphasises body cells rather than embryonic cells.

Verification / Alternative check:
Descriptions of the cloning of the long tailed macaques explain that researchers took nuclei from fibroblast cells, which are somatic cells, and introduced them into enucleated egg cells. This method is clearly labelled somatic cell nuclear transfer and is widely compared to the process used for Dolly the sheep. In such reports, polymerase chain reaction is mentioned only as a laboratory tool for verifying genetic identity, not as the cloning method itself. Parthenogenesis and embryonic cell nuclear transfer are described in different contexts and do not match the procedure described for these monkeys.

Why Other Options Are Wrong:
Option a, polymerase chain reaction, is used to amplify DNA fragments in vitro and cannot by itself produce cloned animals.

Option b, parthenogenesis, is a natural or induced process where an egg develops into an organism without fertilisation, and it does not involve transferring a nucleus from a somatic cell.

Option d, embryonic cell nuclear transfer, uses nuclei from embryonic cells rather than from fully differentiated somatic cells, which does not match the body cell description in the question.

Common Pitfalls:
Students may see the word nuclear transfer and quickly pick any option containing nuclear without reading the full description of somatic versus embryonic cells. Others may confuse commonly heard terms like polymerase chain reaction with cloning methods because both are molecular biology techniques. To avoid these errors, focus on the source of the nucleus mentioned in the question. If it clearly refers to a body cell, the method is somatic cell nuclear transfer, which is the classic cloning technique used in these high profile experiments.

Final Answer:
The macaque monkeys were cloned by Somatic cell nuclear transfer.