In genetics, which statement best defines a “clone” when referring to an organism produced by cloning techniques?
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AAn artificial life form created from nonliving matter
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BAn offspring genetically identical to both parents in every cell
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CAn offspring whose entire cellular genome is identical to that of one parent (the donor)
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DA particular breed of sheep only
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EAny organism produced by in vitro fertilization
Answer
Correct Answer: An offspring whose entire cellular genome is identical to that of one parent (the donor)
Explanation
Introduction / Context:Cloning in biology refers to producing genetically identical copies of a biological entity. In animals, this typically means making an organism whose nuclear genome matches that of a single donor. The question tests precision in the definition of a clone at the whole-organism level.
Given Data / Assumptions:
- Somatic cell nuclear transfer (SCNT) can generate cloned offspring.
- Clones share nuclear DNA with a single donor; mitochondrial DNA may differ due to oocyte cytoplasm.
- “Identical to both parents” is biologically impossible in sexual reproduction.
Concept / Approach:A cloned organism derives its nuclear genome from one parent (the donor nucleus), not from two gametes. Thus, the correct definition emphasizes complete genetic identity to a single source genome in all cells (allowing for mitochondrial exceptions and somatic mutations post-development).
Step-by-Step Solution:
Exclude options that invoke “both parents” or nonbiological constructs.Identify the statement that specifies identity to one donor across all cells.Select that definition as the best description of a clone.Verification / Alternative check:Classic examples (e.g., Dolly the sheep) confirm nuclear genetic identity to the donor ewe supplying the somatic nucleus, not to both parents.
Why Other Options Are Wrong:
- Artificial life form: not a scientific definition of cloning.
- Identical to both parents: contradicts the concept.
- Breed-specific: cloning is not limited to one species or breed.
- IVF offspring are not clones; they are genetically unique.
Common Pitfalls:Confusing IVF with cloning; ignoring mitochondrial DNA differences while focusing on the nuclear-genome concept.
Final Answer:An offspring whose entire cellular genome is identical to that of one parent (the donor)