What is correct?

Options

A. Monosomy and nullisomy are two types of euploidy
B. Polyploidy is more common in animlas than in plants
C. Polyploids occur due to failure in separation of complete sets of chromosomes
D. 2n-1 is trisomy

Answer

To solve the question "What is correct?" regarding the statements about chromosomal abnormalities, we will analyze each option step by step.

### Step-by-Step Solution:

1. **Analyze the first statement:**
- **Statement:** "Monosomy and nullisomy are two types of euploidy."
- **Explanation:** Monosomy (2n-1) and nullisomy (2n-2) refer to conditions where there is a loss of one or two chromosomes, respectively. These conditions are classified as **aneuploidy**, not euploidy. Euploidy refers to changes in complete sets of chromosomes.
- **Conclusion:** This statement is **incorrect**.

2. **Analyze the second statement:**
- **Statement:** "Polyploidy is more common in animals than in plants."
- **Explanation:** Polyploidy involves the presence of more than two complete sets of chromosomes. It is much more common in plants than in animals due to the nature of plant reproduction and their ability to tolerate such changes.
- **Conclusion:** This statement is **incorrect**.

3. **Analyze the third statement:**
- **Statement:** "Polyploidy occurs due to failure in separation of complete sets of chromosomes."
- **Explanation:** Polyploidy can occur when there is a failure in the separation of chromosomes during cell division (mitosis or meiosis), leading to daughter cells with multiple sets of chromosomes.
- **Conclusion:** This statement is **correct**.

4. **Analyze the fourth statement:**
- **Statement:** "2n-1 is trisomy."
- **Explanation:** Trisomy refers to the condition where there is an extra chromosome, represented as 2n+1. Monosomy is represented as 2n-1, indicating the loss of one chromosome.
- **Conclusion:** This statement is **incorrect**.

### Final Conclusion:
The only correct statement among the options provided is the third one: "Polyploidy occurs due to failure in separation of complete sets of chromosomes."

---