In one series of insects males have 17 chromosomes while female have 18 chromosomes. The type of sex determination in that species is

Options

A. ZO type
B. ZW type
C. XY type
D. XO type

Answer

To determine the type of sex determination in the given series of insects where males have 17 chromosomes and females have 18 chromosomes, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Chromosome Numbers**:
- The question states that males have 17 chromosomes and females have 18 chromosomes. This indicates that females possess one more chromosome than males.

2. **Identifying Sex Determination Systems**:
- There are several known sex determination systems, including:
- X-Y system (common in mammals)
- Z-W system (common in birds)
- X-O system (common in some insects)
- Z-O system (less common)

3. **Analyzing the X-Y System**:
- In the X-Y system, males typically have one X and one Y chromosome (XY), while females have two X chromosomes (XX). This system does not fit our case since males would have 17 chromosomes (not possible with XY).

4. **Analyzing the Z-W System**:
- In the Z-W system, males are typically ZZ (homozygous) and females are ZW (heterozygous). This system is primarily observed in birds, not insects, so it can be ruled out.

5. **Analyzing the X-O System**:
- In the X-O system, males have one sex chromosome (X) and females have two (XX). This is common in certain insects. If we assume males have 17 chromosomes (16 autosomes + 1 X), then females would have 18 chromosomes (16 autosomes + 2 X), which fits perfectly with the given information.

6. **Conclusion**:
- Based on the analysis, the type of sex determination in this species of insects is the X-O system. Therefore, the correct answer is option 4: X-O type.

### Final Answer:
The type of sex determination in that species is **X-O type**.