Question at position 1 All of the different cell types within a person's body have different genes.are genetically identical.perform all of the same functions.have exactly the same cell structure.Clear my selection

Question

Question at position 1 All of the different cell types within a person's body have different genes.are genetically identical.perform all of the same functions.have exactly the same cell structure.Clear my selection

BlackTom AI · Accepted Answer

All somatic cells in an individual originate from the single fertilized egg and therefore contain the same nuclear DNA sequence; in that sense they are genetically identical.

1. Relevant knowledge points and concepts
- Genome vs. gene expression: Every somatic cell (except rare exceptions) contains the same set of genes (the same genome) inherited from the zygote.  
- Cell differentiation: Different cell types arise because different subsets of those genes are expressed (turned on or off) in each cell type.  
- Structure and function follow gene expression: Morphology and specialized functions depend on which proteins a cell produces.  
- Exceptions: Somatic mutations, immune cell receptor rearrangements, and differing mitochondrial DNA are limited exceptions but do not change the overall principle.

2. Step-by-step reasoning process
- A sperm and egg fuse to form a zygote with one complete genome.  
- The zygote divides repeatedly by mitosis; mitosis copies the same nuclear DNA into daughter cells, preserving the genetic sequence.  
- As development proceeds, cells receive signals that cause epigenetic changes and selective gene expression, producing different proteins.  
- Different proteins produce different cell shapes and functions (e.g., neuron vs. muscle cell) even though the underlying gene set is the same.

3. Calculations
- No numerical calculations are required; the logical chain (zygote → mitosis copies DNA → same genome in somatic cells) suffices.

4. Why the correct answer is correct
- “Are genetically identical” matches the fact that somatic cells share the same nuclear DNA sequence. Differences among cell types are due to regulation of gene expression, not different genes.

5. Why the other options are incorrect
- “Have different genes.” Incorrect because gene content (the genome) is the same across somatic cells.  
- “Perform all of the same functions.” Incorrect; cells are specialized (e.g., red blood cells carry oxygen, neurons transmit signals).  
- “Have exactly the same cell structure.” Incorrect; cellular morphology varies widely across cell types.

6. Conclusion
Therefore, the best answer is “are genetically identical.” This matches the provided correct answer.

Question at position 1 All of the different cell types within a person's body have different genes.are genetically identical.perform all of the same functions.have exactly the same cell structure.Clear my selection单项选择题

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