Define euploidy.

Answer

**Step-by-Step Solution:**

1. **Understanding Chromosomes**: Begin by recognizing that chromosomes are structures within cells that contain DNA, which carries genetic information. In humans, for example, there are 46 chromosomes organized into 23 pairs.

2. **Defining Euploidy**: Euploidy refers to a type of chromosomal variation where there is a change in the complete set of chromosomes. This means that the entire set of chromosomes is either increased or decreased.

3. **Types of Euploidy**:
- **Haploidy**: This is when there is one complete set of chromosomes (n). For example, gametes (sperm and egg cells) are haploid.
- **Diploidy**: This is the normal state for somatic cells, where there are two complete sets of chromosomes (2n).
- **Polyploidy**: This occurs when there are more than two complete sets of chromosomes (e.g., triploid (3n), tetraploid (4n), etc.).

4. **Consequences of Euploidy**: Changes in the number of complete sets of chromosomes can lead to various biological effects, including developmental changes and can even result in sterility in some organisms.

5. **Conclusion**: In summary, euploidy is a chromosomal variation characterized by a change in the number of complete sets of chromosomes, which can involve either a gain or loss of these sets.

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