The condition in which the number of chromosomes changes in multiples of the genome is

Options

A. Polyploidy
B. Trisomy
C. Monosomy
D. Nullisomy

Answer

To solve the question, "The condition in which the number of chromosomes changes in multiples of the genome is," we will analyze each option provided and determine the correct answer.

### Step-by-Step Solution:

1. **Understanding the Question**:
- The question asks for a condition where the number of chromosomes changes in multiples of the genome. This implies that the organism has more than the typical number of chromosome sets.

**Hint**: Think about terms that relate to the number of chromosome sets in an organism.

2. **Analyzing the Options**:
- **Option A: Polyploid**:
- Polyploidy refers to a condition where an organism has more than two complete sets of chromosomes (e.g., triploid, tetraploid). This means the number of chromosomes is indeed changing in multiples of the genome.

**Hint**: Recall that "poly" means many, indicating multiple sets of chromosomes.

- **Option B: Trisomy**:
- Trisomy is a genetic disorder where there are three copies of a specific chromosome instead of the normal two. This does not represent a change in multiples of the entire genome, just an additional copy of one chromosome.

**Hint**: Consider how many sets of chromosomes are involved in trisomy.

- **Option C: Monosomy**:
- Monosomy is a condition where there is only one copy of a particular chromosome instead of two. This is a reduction, not an increase, and does not involve multiples of the genome.

**Hint**: Think about how many chromosomes are present in monosomy.

- **Option D: Nullisomy**:
- Nullisomy refers to the absence of both copies of a particular chromosome. Like monosomy, this is a reduction and does not involve multiples of the genome.

**Hint**: Reflect on what happens to chromosome numbers in nullisomy.

3. **Conclusion**:
- After analyzing all the options, the only condition that fits the description of changing the number of chromosomes in multiples of the genome is **Polyploidy**. Therefore, the correct answer is **Option A: Polyploid**.

### Final Answer:
The condition in which the number of chromosomes changes in multiples of the genome is **Polyploid**.